Red blood cell volume. Causes of the reduced volume of MCV

An indicator of what diseases may be non-compliant red blood cell volume?

An indicator of what diseases may be non-compliant (too low or too high) red blood cell volume? What additional tests should be performed in the case of blood cell volume disorders to confirm or rule out existing diseases?

Usually, in the examination of peripheral blood counts with the use of automatic hematological analyzers, in addition to the quantitative evaluation of morphotic elements, i.e. red blood cells, leukocytes and platelets, the so-called erythrocyte indices, which include: hemoglobin concentration, mean erythrocyte hemoglobin mass (MCH), mean erythrocyte hemoglobin concentration (MCHC) and finally mean erythrocyte volume (MCV).

It is the latter indicator that very often indicates abnormalities related to the hematopoietic system itself or other important tissues, organs or systems. The most common causes of increased MCV include anemia associated with vitamin B deficiency12 and folic acid, myelodysplastic syndromes (a heterogeneous group of neoplastic diseases characterized by ineffective hematopoiesis, which usually leads to peripheral cytopenia – anemia in the first place), hypothyroidism, liver cirrhosis, pregnancy and neonatal age. Finally, vitamin B deficiency itself12 and related anemia can also be secondary to many abnormalities, among which vitamin B deficiency comes to the fore12 and digestive disorders related to alcoholism or veganism, and finally abnormal secretion of pancreatic enzymes (both in the course of pancreatic insufficiency and in the Zollinger-Elison syndrome).

Another very important factor influencing vitamin B deficiency12 are part of the so-called group of factors that result in abnormal secretion of the intrinsic factor IF. It includes a number of abnormalities ranging from congenital deficiency, abnormal structure of the internal factor, through the state after gastrectomy, i.e. removal of the stomach, to histamine-resistant achlorhydria, i.e. Addison-Biermer anemia, which is based on autoimmune phenomena leading to atrophic gastritis (the current antibodies against IF or parietal cells in the stomach). It is worth mentioning that in patients with this disease there is a statistically significant increase in the risk of stomach cancer, as well as endocrine disorders, such as hypothyroidism, myasthenia gravis or adrenal insufficiency. Among the other causes of vitamin B deficiency12 the malabsorption of the vitamin complex should be mentioned. B12-IF due to damage to the distal small intestine. This happens in patients with Crohn’s disease who have had this part of the gut resected and in Imerslund-Grasbeck syndrome (a genetic disorder characterized by poor absorption of vitamin B).12 and proteinuria), with abnormal bacterial flora of the gastrointestinal tract (in the blind loop syndrome, intestinal diverticulosis or tapeworm infection). It is also worth mentioning the drug-induced vitamin B malabsorption12 (this occurs after inhalation of nitric oxide used in anaesthesiology, after long-term use of colchicine, neomycin, metformin or cholestyramine), congenital abnormalities of vitamin B transport12 or intrahepatic metabolism.

The most common causes of reduced MCV include iron deficiency anemia, some anemia of chronic diseases (caused by the action of cytokines that interfere with iron homeostasis and the synthesis of erythropoietin) or thalassemia (usually manifested by hemolytic anemia caused by abnormal synthesis of alpha and beta chains in the hemoglobin molecule). While the last two causes are relatively rare (thalassemia) or are part of anomalies secondary to the underlying disease, most often chronic inflammatory or cancerous diseases (chronic disease anemia), iron deficiency anemia is the most common, about 80% of cases, the cause of the anemia. It is very important that the reduction of MCV secondary to iron deficiency, the lack of which prevents hemoglobin synthesis, is not a disease in itself! However, it is only a manifestation of often very serious irregularities. The main causes of iron deficiency include its loss (through the genital tract – heavy menstruation, postmenopausal bleeding, other pathological bleeding; through the gastrointestinal tract – gastric and duodenal ulcers, hemorrhagic gastropathy, esophageal varices, ruptures of the esophagus / cardia – Mallory-Weiss syndrome. , haemorrhoids, chronic and acute enteritis, colon diverticula, and finally gastrointestinal neoplasms; through the urinary system – mainly tumors and inflammation of the urinary system; through the respiratory tract; also as a result of injuries / operations and in multiple blood donors), increased need (during pregnancy and lactation, in newborns and premature babies fed with mother’s milk, in adolescence, or during the period of increased erythropoiesis during the treatment of vitamin B deficiency12), impaired iron absorption from the gastrointestinal tract (in the course of chronic inflammatory diseases of the gastrointestinal tract, in conditions with decreased acidity of gastric juice, in gluten enteropathy and in an improper diet) and, finally, iron deficiency in food. To sum up, the non-compliant red blood cell volume is not pathognomonic for one disease entity, but may occur in the course of a very wide spectrum of diseases. Therefore, diagnostics dictated by abnormalities in erythrocyte indices, including MCV, should include a number of procedures, ranging from a thorough interview with the patient, through a thorough physical examination, to highly specialized biochemical (including immunological), imaging and endoscopic examinations.

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