Etiopathogenesis and genetic features
Hemophilia develops due to a genetic defect that disrupts the synthesis of key plasma proteins involved in the coagulation cascade. Depending on which specific protein is absent or non-functional, two main forms of the pathology are distinguished:
- Hemophilia A: occurs due to a deficiency of factor VIII.
- Hemophilia B: is caused by a shortage of factor IX.
The disease has a strict genetic linkage. The inheritance pattern is recessive, sex-linked (the gene is localized on the X chromosome). Due to this feature, the clinically expressed form affects only males. The mothers of the patients act as asymptomatic carriers (transmitters) of the defective gene, passing it on to their sons.
Clinical presentation
Manifestation of the disease usually occurs already in childhood. The main feature of hemophilia is a pronounced hemorrhagic syndrome, in which the volume of blood loss completely does not correspond to the severity of the injury. Even a minor bruise can provoke extensive, deep hemorrhage, and a minor trauma can cause prolonged bleeding.
Specific symptoms include:
- Hemarthrosis: massive accumulations of blood in joint cavities. This is one of the most disabling manifestations, as recurrent hemarthrosis inevitably leads to the development of ankylosis (complete immobilization of the affected joint).
- Mucosal and organ bleeding: persistent nosebleeds are characteristic, as well as hematuria (blood in the urine).
Diagnostic algorithm
Diagnosis requires a step-by-step laboratory investigation. At the first stage, differential diagnosis is performed to exclude other causes of bleeding and identify general coagulation disorders. The baseline profile includes:
- Platelet count (allows reliably ruling out thrombocytopenic conditions).
- Assessment of bleeding time.
- Determination of prothrombin time.
- Measurement of aPTT (activated partial thromboplastin time).
In typical cases of hemophilia, it is the aPTT that is found to be isolated and prolonged against the background of normal values of other tests. After identifying this anomaly, one proceeds to the refinement stage:
- Quantitative determination of factors VIII and IX in plasma is performed.
- The diagnosis is confirmed by a decrease in their concentration. In the most severe clinical situations, factor levels drop to critical values (from 0 to 20 IU/L).
Principles of treatment
The evolution of approaches to the treatment of hemophilia has progressed from non-selective methods to targeted replacement therapy.
Historically, the main method of care was the administration of fresh frozen plasma (FFP) to patients. The rationale for this approach was that donor plasma contains the entire physiological spectrum of clotting factors. However, today this method has given way to safer and more effective selective therapy.
Modern tactics are based on the use of preparations containing exclusively the factor that the patient lacks. Drugs of choice include cryoprecipitate and specialized clotting factor concentrates. A differentiated approach is applied:
- Patients with hemophilia A are administered factor VIII concentrates.
- Patients with hemophilia B are prescribed factor IX concentrates.
Briefly: answers to topical questions
How is hemophilia classified by severity depending on the percentage of the deficient factor in the blood?
The classification of hemophilia by severity is based on determining the residual concentration (activity) of the antihemophilic factor in the blood. Depending on this indicator, three degrees of severity of the disease are distinguished:
- Severe degree — factor level is less than 1%.
- Moderate degree — factor level is in the range from 1% to 5%.
- Mild degree — factor level is from 5% to 40%.
Why does the bleeding time remain normal in hemophilia despite the severe hemorrhagic syndrome?
In hemophilia, bleeding time usually remains within the normal range because primary (vascular-platelet) hemostasis is not impaired. Bleeding time reflects the ability of platelets to form a primary white thrombus at the site of vascular injury. Hemophilia refers to a pathology of secondary (coagulation) hemostasis: it is based on a deficiency of plasma blood clotting factors, which is why it is characterized by prolonged blood clotting time. A hematoma-type bleeding pattern with massive hemorrhages into soft tissues and joints is typical for coagulopathies, primarily hemophilia.
Hemophilia A — factor 8 (eight), Hemophilia B — factor 9 (nine). The letters follow the alphabet (A, B), and the factors follow the order of the numbers (8, 9).
Class and exam questions
Do females get hemophilia?
The inheritance pattern is recessive and X-linked. Females have two X chromosomes, so the healthy chromosome compensates for the defective one. They are only carriers (transmitters of the defective gene). Males are affected because they have only one X chromosome.
Which coagulogram parameter changes in hemophilia?
In typical cases, aPTT (activated partial thromboplastin time) is isolated and prolonged. Prothrombin time, bleeding time, and platelet count remain normal.
Why is hemarthrosis dangerous?
Accumulation of blood in a joint (hemarthrosis) in the absence of adequate treatment leads to the development of ankylosis — complete fusion of joint surfaces and loss of mobility (immobilization).
What else to study on this topic
- Mechanisms of ankylosis formation after suffered hemarthrosis
- Differential diagnosis of coagulopathies and thrombocytopenias
- The role of cryoprecipitate in modern clinical practice
- Interpretation and clinical significance of the aPTT parameter
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