Necrotic intestinal lesion
The morphological picture of severe intestinal damage has a number of specific manifestations affecting all layers of the intestinal wall.
- Macroscopic appearance: the affected intestine acquires a characteristic brownish hue. Multiple hemorrhages are observed, and gas accumulates within the wall itself. Fibrin deposition on the peritoneum is detected in the abdominal cavity.
- Microscopic appearance: pronounced edema and areas of hemorrhage predominate in the tissues. Total mucosal necrosis develops, steadily spreading inward to involve the muscular layer. At the same time, inflammatory cellular infiltration is practically absent or extremely weakly expressed.
Twin-to-twin transfusion syndrome
Placental transfusion syndrome is a severe complication occurring in multiple pregnancies. Most frequently, the pathology is registered in monochorionic diamniotic twins, and significantly less often in monochorionic monoamniotic ones.
Pathogenesis of the syndrome The condition is based on the formation of deep pathological arteriovenous anastomoses within the shared placenta. Blood flow is redistributed in such a way that arterial blood enters a placental cotyledon of one twin, but venous drainage is directed into the vascular bed of the second fetus. A one-way blood shunt occurs, forming two opposing roles:
- Donor twin: suffers from insufficient blood supply. It develops pronounced anemia, intrauterine growth restriction (hypotrophy), and oligohydramnios (reduced amniotic fluid volume).
- Recipient twin: receives an excessive blood volume. This leads to hypervolemia, polycythemia, compensatory myocardial hypertrophy, massive edema, and polyhydramnios.
This complication is characterized by pronounced discordance (differences) between the fetuses in body weight, size, and hemoglobin levels. The prognosis is extremely unfavorable, accompanied by high perinatal mortality, with donor twins typically dying intrauterine first.
Non-immune hydrops fetalis
This is a heterogeneous group of severe conditions whose main clinical manifestation is generalized fetal edema unrelated to an immunological conflict (such as Rh factor or ABO system). Morphological changes in organs and tissues depend entirely on the primary disease that caused the hydrops.
Main groups of causes:
- Increased cardiac output: occurs in twin-to-twin transfusion syndrome, placental chorioangioma, truncus arteriosus, cavernous hemangioma, or fetal hyperthyroidism.
- Severe fetal anemia: may result from β-glucuronidase deficiency, congenital leukemia, hereditary hemoglobinopathies, hemolytic anemia, parvovirus B19 infection, intraventricular hemorrhages, massive fetomaternal hemorrhage, or glucose-6-phosphate dehydrogenase deficiency.
- Infectious lesions: toxoplasmosis, rubella, cytomegalovirus infection (CMV), herpes simplex virus (HSV), syphilis, adenovirus infection.
- Genetic and chromosomal abnormalities: trisomies (chromosomes 21, 18, 13), Turner syndrome, triploidy, Noonan syndrome, various skeletal dysplasias, congenital arthrogryposis, and multiple pterygium syndrome.
- Vascular anatomy disruption and compression: congenital cystic adenomatoid malformation of the lung, diaphragmatic hernia, mediastinal teratoma, premature closure of the ductus arteriosus, absence of the ductus venosus, renal vein thrombosis.
- Lymphatic obstruction: cystic hygroma or decreased fetal motor activity (e.g., in congenital muscular dystrophy).
- Storage diseases (metabolic): Gaucher disease, Tay-Sachs disease, Niemann-Pick disease, mucolipidosis type 1.
Inborn errors of metabolism
Inborn errors of metabolism are an extensive group (over 400 nosologies) of hereditary pathologies in which the normal course of biochemical reactions in the body is disrupted. The diseases are characterized by a wide spectrum of clinical manifestations, various ages of onset, and diverse morphology.
The overwhelming majority of these pathologies are inherited in an autosomal recessive manner, while X-linked forms are much less common. The basis is a qualitative or quantitative genetic defect in specific enzymes (cytoplasmic, lysosomal, peroxisomal) or transport proteins.
Cellular damage mechanisms:
- Excessive, pathological accumulation of the precursor substance.
- Toxic effect of intermediate metabolites.
- Acute deficiency of the end product of the biochemical reaction.
Diseases in which unbranched metabolic products massively accumulate in the cells of various tissues are called storage diseases (thesaurismoses). Clinically, they are generally divided into groups with predominant central nervous system involvement, hepatocellular diseases, myopathies, and nephropathies. However, certain pathologies (homocystinuria, familial hypercholesterolemia, Lesch-Nyhan syndrome) have a unique phenotype and do not fit into such a strict classification.
Phenylketonuria: pathogenesis and clinical features
Phenylketonuria is a severe autosomal recessive disease based on a profound disruption of the metabolism of the essential amino acid phenylalanine. Early screening and timely initiation of dietary therapy play a decisive role in the child's prognosis for life and development.
Etiology and pathogenesis: The underlying cause of the classical form is a congenital deficiency of the enzyme phenylalanine hydroxylase. Atypical forms also occur (up to 10% of cases) associated with a shortage of other enzymes (e.g., dihydropteridine reductase). Due to the enzymatic block, the normal conversion of phenylalanine to tyrosine is disrupted. The concentration of phenylalanine itself and its deamination products (phenylpyruvic, phenyllactic acids, and phenylacetate) rapidly increases in the patient's blood, urine, and sweat. It is precisely these metabolites that exert a pronounced toxic effect on the developing central nervous system.
Clinical manifestations: Immediately after birth, infants look completely healthy. Manifestation of the disease begins shortly after the first feedings, when protein containing phenylalanine enters the body via maternal breast milk. Persistent neurological symptoms develop, reaching their maximum by 3 years of age.
Three main groups of symptoms are distinguished:
- Mental retardation (ranging from moderate degree to profound disability).
- Severe neurological symptoms: muscle hypertonia, pronounced tremor, ataxia, various movement disorders (hyperkinesia), and epileptiform seizures.
- Hypopigmentation: arises due to impaired melanin synthesis (caused by the block in the transition of phenylalanine to tyrosine). Children have a characteristic appearance: very fair hair, pale skin, and blue eyes. The skin of such patients has increased sensitivity to ultraviolet light and is prone to developing severe dermatitis and eczema.
Briefly: answers to topical questions
What are the macroscopic manifestations of necrotic intestinal lesions in rickets?
Macroscopic manifestations of necrotic intestinal lesions in rickets are characterized by specific changes in the organ's color, the presence of hemorrhages, and gas accumulation.
- Intestine — acquires a characteristic brownish color, hemorrhages are visualized on it, and air is contained within the thickness of the intestinal wall.
- Peritoneum — covered with fibrin on its surface.
What causes non-immune hydrops fetalis?
Non-immune hydrops fetalis is caused by an extensive group of pathological conditions not related to an immunological conflict.
- Increased cardiac output — twin transfusion syndrome, placental chorioangioma, hyperthyroidism.
- Fetal anemia — congenital leukemia, hemoglobinopathies, parvovirus B19, massive fetomaternal hemorrhage.
- Infections — toxoplasmosis, rubella, cytomegalovirus, syphilis.
- Genetic anomalies — trisomy 21, 18, 13, Turner syndrome, skeletal dysplasias.
- Thoracic vessel compression — chylothorax, diaphragmatic hernia, mediastinal teratoma.
- Vascular anomalies — renal vein thrombosis, umbilical cord vessel compression.
- Lymphatic vessel obstruction — cystic hygroma.
- Metabolic diseases — Gaucher disease, Hurler syndrome, lysosomal storage diseases.
Idiopathic hydrops of undetermined etiology is also distinguished.
What is the pathogenesis of twin-to-twin transfusion syndrome?
The pathogenesis of twin-to-twin transfusion syndrome is based on the formation of deep arteriovenous anastomoses in the placenta. The placental lobule of one twin receives arterial blood from its own share, whereas venous drainage occurs into the circulatory system of the other twin. As a result of this unidirectional blood shunt, a hemodynamic imbalance arises: one fetus becomes the donor, losing circulating blood volume, while the second fetus becomes the recipient, receiving an excess blood volume. This condition is a severe complication of multiple pregnancy and develops predominantly in monochorionic diamniotic and monoamniotic twins.
How do the donor twin and recipient twin differ in twin-to-twin transfusion syndrome?
The donor twin and recipient twin in twin-to-twin transfusion syndrome exhibit marked discordance in mass, size, and hemoglobin levels.
| Sign | Donor twin | Recipient twin |
|---|---|---|
| Blood volume and hemoglobin | Anemia | Hypervolemia, polycythemia |
| Physical development | Hypotrophy | Cardiac hypertrophy, edema |
| Amniotic fluid | Oligohydramnios (decreased volume) | Polyhydramnios |
This condition is accompanied by high mortality, with donor twins dying first.
What are the main mechanisms of cell damage in congenital metabolic disorders?
The main mechanisms of disorders in inborn errors of metabolism are associated with qualitative or quantitative defects of enzymes or transport proteins:
- excessive accumulation of the precursor substance;
- accumulation of toxic metabolites;
- deficiency of the final reaction product.
Storage diseases, or thesaurismoses, are characterized by the accumulation of aberrant metabolic products in cells and tissues.
What type of inheritance is typical for most inborn errors of metabolism?
Most inborn errors of metabolism are characterized by a recessive inheritance pattern. Autosomal recessive inheritance is most common, while X-linked inheritance is rarer. Currently, more than 400 such anomalies are known.
What are the causes and pathogenesis of phenylketonuria?
The cause of phenylketonuria is an autosomal recessive mutation leading to a deficiency of the enzyme phenylalanine hydroxylase (or phenylalanine-4-hydroxylase), and in atypical cases, dihydropteridine reductase. The pathogenesis of the disease includes the following stages:
- Metabolic blockade — the normal conversion of the essential amino acid phenylalanine to tyrosine is impaired.
- Metabolite accumulation — the levels of phenylalanine itself and its deamination products (phenylacetate, phenylacetoacetic, and phenylpyruvic acids) increase in blood, urine, and sweat.
- Nervous system damage — the accumulation of these neurotoxic metabolites disrupts the development of the central nervous system.
In the atypical form, a combined disturbance of tyrosine and tryptophan metabolism additionally occurs, leading to impaired neurotransmitter synthesis.
What clinical symptoms are characteristic of phenylketonuria?
Clinical symptoms of phenylketonuria manifest shortly after birth and are grouped into three main categories.
- Intellectual disability — ranges from moderate to severe.
- Neurological symptoms — include muscular hypertonus, tremor, ataxia, hyperkinesia, and epileptiform seizures.
- Hypopigmentation — manifested by fair hair, blue eyes, and pale skin with a tendency toward dermatitis and eczema.
Additionally, a specific "musty" or "mousy" odor is noted due to the excretion of metabolites with sweat. Physical development is affected only slightly, though microcephaly and delayed tooth eruption are possible. The most pronounced symptoms develop by the age of three.
What else to study on this topic
- Mechanisms of arteriovenous anastomosis formation in multiple pregnancy.
- Detailed organ morphology in non-immune hydrops fetalis.
- Pathogenesis of intraventricular hemorrhage in the fetus.
- Classification of lysosomal storage diseases (Gaucher disease, Niemann-Pick disease, Tay-Sachs disease).
- Principles of early neonatal screening for phenylketonuria and other enzymopathies.
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