Diseases of platelets

Platelets, or blood platelets, play a key role in the processes of vascular-platelet hemostasis - the initial stage of thrombus formation.

Platelets are denuclearized blood cells of 1-4 μm in size (young forms of platelets are larger) and a life span of 7-10 days. 1/3 of the platelet is in the spleen and 2/3 - in the bloodstream. The number of platelets in the human peripheral blood varies between 150 000-400 000 / mm ³. The average volume of the platelet is 7.1 femoliters (1x10 ¹⁵ l).

With a decrease in the number of platelets or a violation of their function, bleeding may occur. The most typical bleeding from damaged skin and mucous membranes: petechiae, purpura, ecchymosis, nasal, uterine, gastrointestinal bleeding, hematuria. Intracranial hemorrhages are rare.

The most common cause of thrombocytopenia is the immune destruction of blood platelets by auto-, allo- or drug-induced antibodies.

[1], [2], [3], [4], [5], [6]

Pathophysiological classification of thrombocytopenic conditions

Increased destruction of platelets (with normal or increased number of megakaryocytes in the bone marrow - megakaryocytic thrombocytopenia).

Immune thrombocytopenia

• Idiopathic:
  • ETC.
• ♦ Secondary:
  • are induced by infections, including viral (HIV, cytomegalovirus [CMV], Epstein-Barr, herpes, measles rubella, measles, parotitis, parvovirus B19) and bacterial (tuberculosis, typhus);
  • drug-induced;
  • posttransfusion purpura;
  • autoimmune hemolytic anemia (Fischer-Evans syndrome).
  • systemic lupus erythematosus;
  • hyperthyroidism;
  • lymphoproliferative diseases;
  • allergy, anaphylaxis.
• Congenital immune thrombocytopenia:
  • congenital trans-symmetric thrombocytopenia;
  • congenital alloimmune thrombocytopenia;
  • fetal erythroblastosis - Rh-incompatibility.

Non-immune thrombocytopenia

• Caused by increased consumption of platelets:
  • microangiopathic hemolytic anemia;
  • DIC-syndrome;
  • chronic recurrent schizocytic hemolytic anemia;
  • hemolytic-uremic syndrome;
  • TTP;
  • the Kazabaha-Merritt syndrome (giant hemangioma);
  • "Blue" heart defects.
• Caused by increased destruction of platelets:
  • medicinal (ristocetin, protamine sulfate, bleomycin, etc.);
  • stenosis of the aorta;
  • infection;
  • cardial (artificial valves, repair of intracardiac defects, etc.);
  • malignant hypertension.

Violation of the distribution and deposition of platelets

• Hyperplenism (portal hypertension, Gaucher's disease, congenital "blue" heart defects, neoplasms, infections, etc.)
• Hypothermia.

Decreased platelet production (decrease or absence of megakaryocytes in the bone marrow - amygakaryocytic thrombocytopenia)

Hypoplasia or depression of megakaryocytes 1

• Medicinal (chlorothiazides, estrogens, ethanol, tolbutamide, etc.).
• Constitutional:
  • thrombocytopenia with TAR-syndrome (congenital absence of radial bones);
  • congenital platelet hypoplasia without abnormalities;
  • congenital hypoplastic thrombocytopenia with microcephaly;
  • rubella embriofetopathy;
  • trisomy 13,18;
  • Fanconi anemia.
• Ineffective thrombocytopoiesis:
  • megaloblastic anemia (deficiency of vitamin B ₁₂ and folic acid);
  • severe iron deficiency anemia;
  • hereditary thrombocytopenia;
  • paroxysmal nocturnal hemoglobinuria.
• Disorders of regulation of thrombocytopoiesis:
  • insufficiency of thrombopoietin;
  • intermittent dysgenesis of platelets;
  • cyclic thrombocytopenia.
• Metabolic disorders:
  • methylmalonic acidemia;
  • ketone glycineemia;
  • deficiency of carboxyl synthetase;
  • isovaleric acidemia;
  • idiopathic hyperglycinemia;
  • Newborns from mothers with hypothyroidism.
• Hereditary diseases of platelets 2:
  • the Bernard-Soulier syndrome;
  • the May-Heglin anomaly;
  • Wiskott-Aldrich syndrome;
  • linked to the sex of thrombocytopenia;
  • Mediterranean thrombocytopenia.
• Acquired aplastic diseases:
  • idiopathic;
  • drug-induced (overdose of antitumor drugs, organic and inorganic arsenic, mezantoin, trimethine, antithyroid, anti-diabetic, antihistamines, butadione, insecticides, gold preparations, idiosyncrasy to levomycetin);
  • radiation;
  • virus-induced (hepatitis, HIV, Epstein-Barr virus, etc.).

Infiltrative processes in the bone marrow

• Benign:
  • osteopetrosis;
  • accumulation diseases.
• Malignant:
  • neoplasms: leukemia, myelofibrosis, Langer- cell-cell histiocytosis.
  • secondary: lymphomas, neuroblastoma, metastasis of solid tumors.

With a decrease in the number of megakaryocytes in the bone marrow, in addition to aspiration, bone marrow biopsy is required to prevent typical errors. These conditions are associated with a normal or increased amount of megakaryocytes in the bone marrow.