Acquired pure red cell aplasia (erythroblastopenia): clinical guidelines

List of Abbreviations

PRCA – pure red cell aplasia

DBA – Diamond-Blackfan anemia

HIV – human immunodeficiency virus

DNA – deoxyribonucleic acid

MDS — myelodysplastic syndrome

AIHA – autoimmune hemolytic anemia

TIBC – total iron-binding capacity

TS – transferrin saturation

T-LGLL – T-cell large granular lymphocyte leukemia

CLL – chronic lymphocytic leukemia

Allo-HSCT – allogeneic hematopoietic stem cell transplantation

GVHD – graft-versus-host disease

Terms and Definitions

Pure red cell aplasia (PRCA) is a syndrome characterized by an isolated reduction of erythroid precursors in the bone marrow (erythroblasts <5%), manifesting as isolated hyporegenerative anemia.

Diamond-Blackfan anemia is a rare form of congenital bone marrow failure, predominantly affecting the erythroid lineage, occurring in early childhood as a result of a ribosome biogenesis defect accompanied by apoptosis of erythroid precursors in the bone marrow.

Anemia is a decrease in hemoglobin concentration and red blood cell count.

Hyporegenerative anemia is an anemia presenting with absolute reticulocytopenia.

Parvovirus B19 is a DNA virus of the Parvoviridae family with tropism for the membrane receptor of erythroid cells.

Myelodysplastic syndrome is a heterogeneous group of clonal hematopoietic stem cell disorders characterized by cytopenia, dysmyelopoiesis, and a high risk of transformation into acute leukemia.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

PRCA is a syndrome characterized by an isolated reduction of erythroid precursors in the bone marrow (erythroblasts <5%), which manifests as the development of isolated hyporegenerative anemia [1, 2].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

PRCA is a rare hematological syndrome resulting from various pathophysiological mechanisms. Acquired and congenital forms of PRCA are conventionally distinguished [1, 3]. The congenital form of PRCA is Diamond-Blackfan anemia, which has a number of unique pathophysiological and phenotypic differences from acquired variants of PRCA. The pathogenesis of Diamond-Blackfan anemia, inherited in an autosomal dominant manner, is based on mutations or deletions of genes regulating ribosome biogenesis, leading to macrocytic hypo- or aregenerative anemia and congenital malformations (most commonly craniofacial, upper limb, cardiac, and urogenital anomalies); the disease debuts in early childhood [4].

A special infection-mediated form of PRCA is transient aplastic crisis caused by parvovirus B19, a condition characteristic of immunologically compromised patients (e.g., in HIV infection or severe combined immunodeficiency), as well as patients with hereditary hemolytic anemias [5]. The tropism of parvovirus B19 for erythroid precursors is due to the virus's ability to bind to membrane P antigen (cases of resistance to parvovirus B19 are known in patients whose erythroid precursors do not express this antigen) [6]. It is hypothesized that individual cases of PRCA, especially in immunodeficient patients, may have a pathogenetic relationship with Epstein-Barr virus or cytomegalovirus replication (indirectly confirmed by the efficacy of intravenous immunoglobulin therapy in PRCA patients without parvovirus B19 replication); however, in most cases, the viral agent remains unidentified.

In children, the most frequent variant of PRCA is transient erythroblastopenia of childhood (TEC). This is a benign disease, most commonly observed at the age of 18–26 months, although it has been described in infants under 6 months and in children older than 10 years. The etiology of this disease is unknown, with a putative triggering role of viral infection [7].

Except for DBA and parvovirus B19-associated transient aplastic crisis, the majority of PRCA cases are considered idiopathic (primary) and pathogenetically linked to T-lymphocyte autoaggression directed against early erythroid precursors in the bone marrow under the action of unknown triggers [1, 8, 9]. This concept is supported by the efficacy of immunosuppressive therapy targeting T lymphocytes.

In addition, PRCA is known to be associated with a number of diseases, in the presence of which PRCA is considered secondary:

• PRCA in autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, etc.) [10];

• PRCA following allo-HSCT [11];

• PRCA associated with lymphoproliferative disorders (chronic lymphocytic leukemia, large granular lymphocytic leukemia, Hodgkin lymphoma, non-Hodgkin lymphomas, etc.) [12–14];

• PRCA associated with other oncohematological diseases (chronic myeloid leukemia, etc.) [15];

• PRCA associated with solid tumors (thymoma, etc.) [16];

• PRCA associated with infections (parvovirus B19, HIV, viral hepatitis B and C, tuberculosis, etc.) [5];

• drug-induced PRCA (Epoetin alfa** and other drugs – Table 1) [1, 17];

• PRCA associated with pregnancy [18].

Table 1. Medications associated with the development of secondary PRCA (according to a PubMed database review. Includes drugs registered in Russia with more than one mention in scientific publications).

1.3 Epidemiology of the Disease or Condition

PRCA is a rare disease, therefore the number of epidemiological studies is limited. According to a mono-ethnic study, the incidence of acquired PRCA is 1.06 cases per 1 million population per year [19].

According to a study from the USA generalizing the follow-up results of 62 patients with PRCA over 16 years, the median age of patients was 62 years (range 25–87 years), 52% of patients had idiopathic PRCA, while thymoma- and large granular lymphocyte leukemia-associated PRCA were registered less frequently [20].

A number of publications report the frequency of secondary PRCA in various nosologies. In particular, PRCA was a complication in 1.8–14.3% of patients with thymoma [21–24], 28.8–68.2% of patients with large granular lymphocyte leukemia [25–27], 0.5–1.5% of patients with chronic lymphocytic leukemia [28, 29], and 7.5–10.5% of patients after allo-HSCT [11, 30].

1.4 Features of Coding the Disease or Condition

The codes assigned to acquired pure red cell aplasia (erythroblastopenia) in the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10), are presented in Table 2. [31]

Table 2. ICD-10 codes assigned to acquired pure red cell aplasia (erythroblastopenia).

1.5 Classification of the disease or condition

Currently, there is no unified classification of PRCA that takes into account all classification features, including etiology, disease pathogenesis, and clinical phenotype characteristics.

Russian literature uses the 1997 classification (Table 3) [32].

Table 3. National classification of PRCA from 1997.

In foreign publications, the classification by Wintrobe and Darry M. Williams as modified by J. Lipton et al. is most widely used (Table 4) [1, 3].

Table 4. Classification of PRCA proposed by Wintrobe and Darry M. Williams, modified by J. Lipton.

1.6 Clinical presentation of the disease or condition

There is no specific clinical picture for idiopathic (primary) PRCA. Patients report symptoms of hypoxic syndrome, including pallor, palpitations, tinnitus, headache, weakness, and decreased exercise tolerance. A gradual decrease in hemoglobin concentration may contribute to adaptation to anemia, as a result of which hypoxia symptoms may be less pronounced [1].

In patients with secondary PRCA, symptoms caused by the underlying disease may dominate the clinical picture [1].

In patients with PRCA receiving a massive blood transfusion load and lacking adequate chelation therapy, symptoms due to secondary hemochromatosis may be observed: skin and mucosal pigmentation, endocrinopathy (most commonly diabetes mellitus, hypothyroidism, hypogonadism), cardiac arrhythmias, arthralgia, and the development of liver cirrhosis [33].

2. Diagnostics, medical indications and contraindications for diagnostic methods

The diagnosis of PRCA is based on the characteristic clinical and laboratory findings of the disease and is verified by bone marrow examination results demonstrating a partial reduction in erythroid precursors.

2.1 Complaints and Anamnesis

See the "Clinical Presentation" section

2.2 Physical Examination

Comments: during the physical examination, attention should be paid to the following signs and symptoms of the disease:

• manifestations of anemic syndrome (weakness, dizziness, headache, decreased exercise tolerance, pallor of the skin and visible mucous membranes, tachycardia);

• presence of lymphadenopathy, splenomegaly, superior vena cava compression syndrome for differential diagnosis with lymphoproliferative disorders;

• presence of symptoms of tumor intoxication (fever, profuse night sweats, weight loss >10% over 6 months) typical of hemoblastoses and solid tumors;

• cough, shortness of breath, chest pain, dysphagia, manifestations of compression syndrome, cardiac arrhythmias, choking attacks, cyanosis typical of thymoma;

• signs of multiorgan involvement typical of systemic connective tissue diseases (including involvement of the skin and mucous membranes, joints and muscles, lungs, kidneys, nervous system);

• presence of congenital malformations characteristic of Diamond-Blackfan anemia (skull development anomalies, including: hypertelorism, high arched palate, cleft palate, flat nasal bridge, micrognathia, microcephaly, microtia, low-set ears; hand anomalies; urogenital system pathology).

• symptoms of secondary hemochromatosis, including skin and mucosal pigmentation, endocrinopathy (most commonly diabetes mellitus, hypothyroidism, hypogonadism), cardiac arrhythmias, arthralgia, and the development of liver cirrhosis.

2.3 Laboratory Diagnostics

Comments: Acquired PRCA is characterized by the development of isolated normochromic, normocytic anemia with a sharp decrease in reticulocyte count (typically less than 10,000 cells/µL, relatively <1%). Platelet and leukocyte counts and the leukocyte differential are unchanged in idiopathic PRCA, whereas in secondary PRCA they depend on the nature of the underlying disease [1, 2].

- blood total bilirubin level test, free and conjugated bilirubin level test, and blood lactate dehydrogenase activity assay for the differential diagnosis of PRCA with hemolytic anemias;

- blood creatinine level test, blood urea level test, and blood erythropoietin level test to rule out kidney disease-associated anemia;

- blood vitamin B12 (cyanocobalamin) level test and serum folic acid level test to rule out a deficiency state as a cause of hyporegenerative anemia.

GCR CLoE 3Grade of Recommendation C (Level of Evidence – 3)

Comments: Patients with PRCA who are dependent on transfusion replacement therapy are at high risk of developing secondary hemochromatosis [9, 37]. To ensure timely diagnosis of this condition, laboratory iron metabolism parameters must be monitored. If signs of secondary hemochromatosis are detected, iron chelation therapy is indicated (Section 3.1 – Conservative treatment).

Comments: verification of PRCA diagnosis is based on bone marrow examination. In idiopathic (primary) PRCA, bone marrow cellularity is normal. A pathognomonic sign of PRCA is the virtually complete absence of erythroblasts in the bone marrow (<1% erythroblasts on differential cell count) in the absence of anomalies in other hematopoietic lineages [1, 2, 9]. In some cases, a small number of proerythroblasts and/or basophilic erythroblasts may be detected, not exceeding a total of 5% of the differential cell count. Large proerythroblasts with vacuolated cytoplasm and pseudopodia are an indirect sign of parvovirus B19-associated PRCA [1].

Comments: in idiopathic (primary) PRCA, cytogenetic abnormalities are absent. The detection of clonal aberrations characteristic of MDS rules out the diagnosis of primary (idiopathic) PRCA.

Comments: T-LGL is the most frequent cause of secondary acquired PRCA, occurring in 15–20% of cases [25–27].

Comments: specifics of laboratory diagnostic tests for PRCA after allogeneic hematopoietic stem cell transplantation [39, 40]:

It presents at +2 months post allo-HSCT, after ruling out viral infections (parvovirus B19, herpesviruses), disease relapse, drug toxicity, iron, folate, and vitamin B₁₂ deficiency. Most commonly develops in major ABO incompatibility between recipient and donor post allo-HSCT, occurring in 30% of major incompatibility cases (Table 5).

Diagnostic Criteria:

• Normocytic anemia requiring red blood cell transfusions.

• Absence of reticulocytosis in peripheral blood (less than 1%).

• Reduction or complete absence of the erythroid lineage on bone marrow cytology (less than 5%).

• Donor chimerism of 95–100%.

• Elevation of peripheral blood isohemagglutinin titers by more than 2-fold from baseline.

Table 5. Types of incompatibility according to donor-recipient blood group pairs

2.4 Instrumental Diagnostics

Comments: the detection rate of thymoma in patients with PRCA ranges from 7 to 10%. PRCA may either precede the diagnosis of thymoma or develop after thymectomy. Artificial intelligence technologies can be used for image interpretation (if available and adapted for thymoma diagnostics).

2.5 Other Procedures

No.

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

3.1 Conservative Treatment

The goal of PRCA treatment is to achieve a normal hemoglobin concentration without the need for red blood cell transfusions. Partial response is defined as achieving transfusion independence with a clinically acceptable hemoglobin concentration [1].

Immunosuppressive therapy is used as first-line therapy in patients with idiopathic (primary) PRCA and secondary forms of PRCA associated with T-LGL and solid tumors. Immunosuppressive therapy is also used in patients with secondary PRCA refractory to the treatment of the underlying disease [8, 41, 42]. The drug of choice in the treatment of parvovirus B19-associated PRCA is intravenous immunoglobulin (#normal human immunoglobulin**) [5, 43].

Most children with transient erythroblastopenia of childhood, even with severe anemia, recover spontaneously within 1–2 months of disease onset, and therefore therapy is not required [7]

Treatment of patients with secondary PRCA begins with therapy for the underlying disease. If an infectious disease associated with PRCA development is diagnosed (HIV infection, viral hepatitis, tuberculosis, etc.), specific therapy for that disease is administered. Similarly, if PRCA complicates the course of CLL, Hodgkin lymphoma, non-Hodgkin lymphoma, or another lymphoproliferative disorder, anti-tumor therapy is indicated [1]. If the patient is taking medications associated with PRCA development (Table 1), consideration should be given to discontinuing the drug [1, 44].

Pregnancy-associated PRCA is a rare syndrome and generally resolves after pregnancy termination. Some patients require replacement transfusion therapy, a specific indication for which is fetal oxygenation impairment. It is recommended to avoid immunosuppressants during pregnancy due to potential adverse effects on the fetus (with the exception of #prednisolone**) [18].

Comments: specific antiviral therapy for parvovirus B19 infection is currently unavailable. Therapy with #normal human immunoglobulin** is highly effective in parvovirus-associated PRCA; however, ⅓ of patients may experience PRCA relapses requiring repeated courses of therapy. Patients with confirmed immunodeficiency states should receive replacement therapy with #normal human immunoglobulin** on a continuous basis in accordance with clinical guidelines for the treatment of primary and secondary immunodeficiencies.

Comments: the daily dose of #cyclosporine** is divided into two doses at 12-hour intervals. Blood drug concentration monitoring is required during #cyclosporine** therapy. The target blood concentration of #cyclosporine** is 150–250 ng/ml. Dose adjustments, either upward or downward, may be made to achieve optimal concentration. The potential nephrotoxic effect of #cyclosporine** must be kept in mind, and it should be used with caution in patients with impaired renal function.

After achieving a response, it is advisable to rapidly taper the dose of #prednisolone** followed by complete discontinuation.

The exact duration of #cyclosporine** therapy has not yet been established, but as a rule, gradual tapering is initiated no earlier than 4–6 months after achieving a response. Some patients may develop #cyclosporine** dependency, requiring long-term maintenance therapy. #Cyclosporine** is tapered gradually by 25–50 mg (20% of the dose in pediatric patients) per month under the control of complete blood counts.

Comments: the target blood concentration of #sirolimus is 4–15 ng/mL. The optimal duration of therapy is not defined. #Sirolimus may be used in patients with impaired renal function, as it has a lesser impact on the glomerular filtration rate compared to #cyclosporine** and is excreted predominantly via the gastrointestinal tract. Liver function tests must be monitored during #sirolimus therapy.

#cyclophosphamide** 50–100 mg/day orally in courses lasting up to 12 months;

GCR BLOE 2Grade of Recommendation B (Level of Evidence – 2).

#methotrexate** 7.5–20 mg orally once weekly [52];

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

#cyclosporine** 3–5 mg/kg/day orally daily.

GCR BLOE 2Grade of Recommendation B (Level of Evidence – 2).

- #rituximab** at a dose of 375 mg/m² intravenously as an infusion, 4 doses [10, 20, 53];

- #bortezomib** at a dose of 1.3 mg/m² subcutaneously, once weekly for 4 weeks [54];

- Equine antithymocyte globulin 40 mg/kg/day, intravenously as an infusion for 4 days [47, 55, 56];

- #methotrexate** 7.5–20 mg, orally, once weekly [20, 52];

GPP CLOE 4Grade of Recommendation C (Level of Evidence – 4).

- #cyclophosphamide** 50–100 mg/day, orally, in courses lasting up to 12 months [47];

- #alemtuzumab** 10 mg weekly, intravenously as an infusion, for 4–6 weeks [20, 47]

Level of Evidence BLevel of Confidence 2Level of recommendation B (level of evidence – 2).

Comments: various immunosuppressants may be used as third-line therapy. Data on the efficacy and optimal regimen of these agents in PRCA are limited. The choice of therapy is made by clinicians based on the patient's performance status and the presence of contraindications to specific drugs.

#Bortezomib** may be effective in PRCA developing after ABO-incompatible allogeneic hematopoietic stem cell transplantation or associated with monoclonal gammopathy [38, 54].

The efficacy of #rituximab** has been described in PRCA associated with lymphoproliferative disorders and post-transplant lymphoproliferative disease [53].

Comments: Allo-HSCT may be considered as salvage therapy in patients with resistant PRCA. The 5-year overall survival after allo-HSCT in PRCA is 51%, and event-free survival is 40% [59]. The decision regarding transplantation should be made by a transplant center experienced in performing allo-HSCT in patients with bone marrow failure syndromes.

Comments: The onset of drug-induced PRCA can range from several days to several months. A list of the drugs most frequently causing PRCA is presented in Table 1. The core management strategy is complete discontinuation of the drug that caused PRCA. If discontinuation is impossible (vital indications), consideration should be given to replacing it with a drug having a different mechanism of action within the same indication. If hematopoiesis does not recover after discontinuation of the suspected drug, immunosuppressive therapy is required.

Management of PRCA after allo-HSCT in patients over 18 years of age:

When choosing a therapeutic approach, it is recommended to consider the risk of relapse of the underlying disease, the presence of graft-versus-host disease (GVHD), and graft failure. Several therapeutic approaches exist: plasma exchange procedures with replacement using AB (IV) group donor plasma in a volume of 2,000 mL, which mechanically removes isohemagglutinins. A similar therapeutic method is selective plasmosorption, performed using immunosorption columns specific for a single antigen (A or B) or simultaneously for two antigens (AB). Procedures are performed 2–3 times a week, for a total of 6–8 procedures. Response is assessed 3–4 weeks after the start of therapy [60, 61].

Administration of #rituximab** at a dose of 150–375 mg/m2 once weekly for 2 doses. Response is assessed in 3–4 weeks [62].

GRC CLEL 4Grade of Recommendation C (Level of Evidence – 4)

Thrombopoietin receptor agonist therapy (ATC B02BX Other systemic hemostatics) – #eltrombopag** at an initial dose of 75 mg daily for the first week, followed by 150 mg/day. Response is assessed in 3–4 weeks [63].

GRC CLEL 4Grade of Recommendation C (Level of Evidence – 4)

Therapy with #daratumumab** – an anti-CD38 IgG1κ monoclonal antibody (ATC L01FC CD38 [cluster of differentiation 38] inhibitors), administered at a dose of 16 mg/kg once weekly for 4 weeks [64, 65].

GRC CLEL 4Grade of Recommendation C (Level of Evidence – 4)

• Donor lymphocyte infusion is recommended in the presence of graft failure and the absence of signs of GVHD [66].

GRC CLEL 4Grade of Recommendation C (Level of Evidence – 4)

• In the event of hematopoietic aplasia combined with PRCA, selected CD34+ cells are used [30, 67].

GRC CLEL 4Grade of Recommendation C (Level of Evidence – 4)

• Administration of antithymocyte globulin**; use of mesenchymal stromal cells; #bortezomib** at a dose of 1.3 g/m² once weekly for 4 doses; glucocorticoids [67].

GDR CLE 5Grade of recommendation C (level of evidence – 5)

3.2 Surgical Treatment

Comments: in patients with thymoma-associated PRCA, thymectomy alone rarely leads to PRCA remission, and in most cases, additional immunosuppressive therapy is required after surgery. Despite this, thymectomy with histological verification of the diagnosis should be performed as the first stage of thymoma-associated PRCA treatment. It should be borne in mind that PRCA may either precede the diagnosis of thymoma or develop after thymectomy.

3.3 Transfusion therapy

Comments: indications for initiating transfusion therapy must be determined by the attending physician on an individual basis. When determining transfusion indications, the presence of comorbid conditions, such as coronary artery disease, should be taken into account, which may require transfusion therapy even with a moderate decrease in hemoglobin. For patients under 18 years of age and pregnant women, leukoreduced red blood cell suspension should preferably be used.

Transfusion therapy for PRCA after allogeneic hematopoietic stem cell transplantation.

Taking into account donor-recipient blood group incompatibility, red blood cell component transfusions are carried out with cross-matching according to the ABO system and Rh factor specified in Tables 6 and 7 [71, 72]

Table 6. ABO compatibility for blood component transfusions in ABO-incompatible allo-BMT and allo-HSCT.

Table 7. Compatibility for transfusions of red blood cell components in patients with Rh-incompatible allo-HSCT and allo-BMT.

3.4 Dietary Therapy

Dietary therapy for patients with PRCA during inpatient treatment at medical organizations is organized in accordance with the current orders of the Russian Ministry of Health, taking into account the patient's somatic status and comorbidity, as well as the presence and severity of cytopenia.

3.5. Other treatment modalities

Not applicable.

4. Medical Rehabilitation and Sanatorium-Resort Treatment

No special rehabilitation methods have been developed for PRCA.

5. Prevention and Dispensary Observation

There are currently no methods for preventing PRCA.

Comments: the frequency of follow-up for PRCA patients after completion of treatment is not strictly regulated. During the first year after treatment completion, patients should be evaluated by a hematologist or pediatric hematologist-oncologist at least once every 3 months. Thereafter, the frequency of follow-up is set individually by the hematologist (pediatric hematologist-oncologist) depending on the patient's general condition and well-being, complications of the therapy, and the achieved therapeutic response, but should not be less than once a year. During follow-up, in addition to physical examination, history taking, and symptom assessment, a complete blood count (CBC) with differential is required. Other diagnostic methods may be used at the discretion of the hematologist or pediatric hematologist-oncologist.

6. Organization of Medical Care

Indications for emergency hospitalization to a medical organization:

1. Severe anemia requiring emergency replacement transfusions of red blood cell components

Indications for planned hospitalization in a medical organization:

1. Administration of prophylactic transfusions of donor blood components

2. Evaluation of the patient to verify the diagnosis, including biopsies and invasive procedures when outpatient assessment is not feasible;

3. Performance of elective surgical procedures;

4. Performance of allo-HSCT.

Indications for patient discharge from a medical organization

1. regression of anemia decompensation symptoms, completion of diagnostic workup to verify PRCA.

7. Additional Information

No.

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

Members of the Association for Assistance in the Development of Hematology and Bone Marrow Transplantation "National Hematological Society"

1. Parovichnikova E.N., MD, General Director, National Research Center for Hematology of the Russian Ministry of Health, Chief Freelance Hematologist of the Russian Ministry of Health

2. Lukina E.A., MD, Professor, Head of the Department of Orphan Diseases, National Research Center for Hematology of the Russian Ministry of Health

3. Ponomarev R.V., PhD, Head of the Sector for the Study of Non-Neoplastic Blood System Diseases, National Research Center for Hematology of the Russian Ministry of Health

4. Latyshev V.D., Head of the Hematology Day Hospital for Patients with Inherited Metabolic Diseases, National Research Center for Hematology of the Russian Ministry of Health

5. Kuzmina L.A., PhD, Head of the Department of Hemoblastosis Chemotherapy and Bone Marrow and Hematopoietic Stem Cell Transplantation, National Research Center for Hematology of the Russian Ministry of Health

6. Koroleva O.M., Hematologist at the Immunochemotherapy Day Hospital Post-Bone Marrow and Hematopoietic Stem Cell Transplantation, National Research Center for Hematology of the Russian Ministry of Health

7. Kulagin A.D., MD, Director of the R.M. Gorbacheva Research Institute of Pediatric Oncology, Hematology and Transplantation, Pavlov First Saint Petersburg State Medical University of the Russian Ministry of Health, Chief Freelance Hematologist of the Northwestern Federal District

Members of the Russian Society of Pediatric Hematologists and Oncologists:

8. Smetanina N.S., MD, Professor, Deputy Director of the Institute of Hematology, Immunology and Cell Technologies, Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology of the Russian Ministry of Health

9. Zubarovskaya L.S., MD, Professor, Deputy Director for Transplantation at the Clinic of the R.M. Gorbacheva Research Institute of Pediatric Oncology, Hematology and Transplantation, Pavlov First Saint Petersburg State Medical University of the Russian Ministry of Health

Conflict of interest: the authors declare no conflict of interest.

Appendix A2. Methodology for Developing Clinical Guidelines

Target audience for these clinical guidelines:

a. Hematologists

b. Oncologists

c. Pediatric hematologists-oncologists

d. General practitioners

e. Pediatricians

f. Surgeons

g. Pediatric surgeons

Methodology for evidence collection

Methods used for the collection/selection of evidence:

• Search for publications in specialized periodical print media

• Search in electronic databases.

Methods used for assessing the quality and strength of evidence:

• Expert consensus;

• The significance of the evidence was evaluated in accordance with the levels of evidence (LE) grading scale for diagnostic methods (Table A1) and for preventive, therapeutic, and rehabilitation methods (Table A2).

Table A1. Levels of evidence (LE) grading scale for diagnostic methods (diagnostic interventions)

Table A2. Levels of evidence (LE) grading scale for preventive, therapeutic, and rehabilitation methods (preventive, therapeutic, and rehabilitation interventions)

Description of the methodology for evidence analysis and recommendation development:

When selecting publications as potential sources of evidence, the methodology used in each study was examined to ensure its compliance with evidence-based medicine principles. The result of this examination influenced the level of evidence assigned to the publication, which in turn affects the strength of the resulting recommendations.

Methodological analysis focused on the study design features that had a significant impact on the quality of results and conclusions.

To eliminate the influence of subjective factors, each study was evaluated independently by at least two independent members of the authoring team. Discrepancies in evaluation were discussed at meetings of the working group of the authoring team for these guidelines.

Based on the evidence analysis, the sections of the clinical guidelines were consistently developed with strength assessment in accordance with the recommendation grading scheme (Table 3).

Methods used to formulate the recommendations:

• Expert consensus;

• Evaluation of the strength of recommendations in accordance with the rating scheme (Table A3).

Table A3. Grades of recommendation (GR) scale for preventive, diagnostic, therapeutic, and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitation interventions)

Final version

For the final version and quality control, the guidelines were re-analyzed by the members of the authoring team, who concluded that all significant comments and feedback from experts had been taken into account, and the risk of bias during development was minimized.

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

These clinical guidelines have been developed taking into account the following regulatory and legal documents:

1. Federal Law No. 323-FZ "On the Fundamentals of Protecting Citizens' Health in the Russian Federation" dated November 21, 2011.

2. Order of the Ministry of Health of the Russian Federation No. 203n dated May 10, 2017 "On Approval of Criteria for Assessing the Quality of Medical Care".

3. Order of the Russian Ministry of Health No. 804n dated October 13, 2017 (as amended on April 16, 2019) "On Approval of the Nomenclature of Medical Services"

4. Decree of the Government of the Russian Federation No. 797 dated June 22, 2019, "On Approval of the Rules for Procurement, Storage, Transportation, and Clinical Use of Donored Blood and Its Components and on Invalidation of Certain Acts of the Government of the Russian Federation"

5. Order of the Russian Ministry of Health No. 1170n dated October 28, 2020, "On Approval of the Rules for Providing Medical Care to the Population in the Field of Transfusiology"

6. Order of the Russian Ministry of Health No. 1148n dated October 26, 2020, "On Approval of Requirements for Organizing the Safety System for Activities of Entities Dealing with Donated Blood and (or) Its Components during Procurement, Storage, Transportation, and Clinical Use of Donated Blood and (or) Its Components."

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

What is pure red cell aplasia (PRCA) of the bone marrow?

PRCA is a rare condition observed predominantly in adult patients. It is characterized by the development of anemia (decreased hemoglobin concentration and red blood cell count) with normal platelet and leukocyte counts. The cause of these disorders is a reduced ability of the bone marrow to produce red blood cells.

What causes PRCA?

Currently, it is believed that the majority of PRCA cases are autoimmune in nature, meaning the development of the disease results from an aggressive attack by the patient's immune system cells (specifically, T-lymphocytes) directed against their own hematopoietic stem cells. In such cases, PRCA is considered primary or idiopathic. However, there are other, rarer causes of PRCA development, which include:

• Autoimmune diseases (such as systemic lupus erythematosus, rheumatoid arthritis, and others);

• Blood system disorders, particularly certain variants of lymphomas;

• Thymus tumors (thymomas);

• Viral infections, particularly parvovirus B19;

• Medication intake that can disrupt red blood cell production in the bone marrow.

When these diseases are diagnosed, PRCA is considered secondary — i.e., developing against the background of an underlying condition.

What symptoms are characteristic of PRCA?

By definition, all patients with PRCA have anemia. Symptoms of anemia include:

• Weakness;

• Skin pallor;

• Dizziness;

• Shortness of breath;

• Palpitations.

In secondary PRCA, other symptoms associated with the underlying disease may also be observed.

How is PRCA diagnosed?

Methods for diagnosing PRCA include:

• Physical examination and medical history (anamnesis) collection;

• Complete blood count (CBC) with differential. This allows for the evaluation of the number and certain morphological features of peripheral blood cells. A decrease in the number of young red blood cells (reticulocytes) is an important diagnostic sign of PRCA. Platelet and leukocyte counts in PRCA are generally normal;

• Bone marrow examination, including bone marrow aspiration and trephine biopsy. Despite the presence of characteristic changes in the complete blood count, a diagnosis of PRCA cannot be established without a bone marrow examination. In PRCA, there is a sharp decrease in the number of erythroid precursors in the bone marrow, which allows the diagnosis to be verified;

• Additional laboratory and instrumental examinations prescribed to determine the cause of PRCA development and select the optimal treatment strategy.

How is PRCA treated?

The goal of PRCA treatment is to restore red blood cell production in the bone marrow. Depending on the cause of PRCA, therapeutic approaches may differ:

• To treat primary (idiopathic) PRCA, as well as certain forms of secondary PRCA, medications that suppress excessive activation of the immune system are used (immunosuppressive therapy);

• To treat PRCA associated with parvovirus B19, intravenous immunoglobulin preparations are used;

• In cases of secondary PRCA, therapy directed against the underlying disease may be effective;

• To maintain hemoglobin concentration, transfusions of red blood cell-containing blood components may be performed according to indications;

• Patients undergoing regular blood transfusions may require iron-chelation therapy.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

No.