Vitamin B12 Deficiency and Addison-Biermer Disease
The classic manifestation of cyanocobalamin deficiency is Addison-Biermer disease (pernicious anemia). The pathogenesis of this condition is rooted in marked gastric mucosal atrophy. This structural alteration predictably leads to a severe shortage of Castle's intrinsic factor, without which intestinal absorption of the vitamin becomes impossible.
Key and most severe neurological complication of this state is funicular myelosis — profound degenerative processes within the spinal cord structures. The symptom complex of funicular myelosis includes:
- Paresthesias (various sensory disturbances).
- Shaky, unsteady gait.
- Diminution of normal reflex responses and the appearance of pathological reflexes.
- Psychiatric disorders (developing in severe and prolonged courses of the pathology).
Hereditary Forms of Deficiency
Genetically determined (inherited) Vitaminum B12 deficiency arises due to congenital defects at various stages of its complex metabolism. The etiology of such states includes impaired synthesis of Castle's intrinsic factor, disruptions in intestinal cobalamin absorption mechanisms, as well as quantitative or structural anomalies of transport proteins — transcobalamins I and II (their complete absence, significant concentration reduction, or functional inefficiency).
Clinical presentation of hereditary deficiency is characterized by three main manifestations:
- Megaloblastic anemia.
- Metabolic acidosis, driven by toxic excess of methylmalonate.
- Reduced efficiency of immunobiological surveillance, making the body extremely vulnerable and promoting frequent infectious diseases.
B12 Hypervitaminemia: Causes and Clinical Significance
In real clinical practice, true hypervitaminosis is extremely rare. Physicians much more frequently encounter the phenomenon of B12 hypervitaminemia — an abnormally high vitamin concentration directly in the blood serum.
Causes of such pathological cyanocobalamin elevation are quite diverse:
- Excessive intake into the body (typically with unjustified medical administration of Vitaminum B12 preparations).
- Massive release of the vitamin from internal tissue stores.
- Overproduction or impaired clearance of transcobalamins.
- Deficiency or complete absence of transcobalamin affinity for the vitamin.
It is important to understand that a high blood vitamin level is a symptomatic sign. It signals the presence of severe, potentially life-threatening pathologies.
Diseases Associated with B12 Excess
Symptomatic hypervitaminemia accompanies a number of serious systemic disorders.
| Pathology Group | Examples of Associated Diseases |
|---|---|
| Oncological | Solid neoplasms, hemoblastoses |
| Hepatobiliary | Hepatoses, including severe liver failure |
| Systemic | Renal disorders, bronchopulmonary pathologies, multiorgan failure |
| Immune and Toxic | Immune autoaggressive forms of pathology, alcoholism |
Hypervitaminemia is not a benign state on its own and may cause a range of side effects. These include various allergic reactions, pronounced hepatotoxic effects, and, upon exposure to large doses of the vitamin, even procarcinogenic action. Resolution of hypervitaminemia is achieved solely by identifying and treating the underlying pathology that led to the vitamin surplus in the blood.