Thrombocytopenia

Thrombocytopenia

Thrombocytopenia is a low platelet count in the peripheral blood and is the most common underlying cause of bleeding. With a decrease in the number of platelets less than 100×109/l, the bleeding time lengthens. In the bulk of cases, petechiae or purpura are found when the number of platelets drops to 20-50 x 109 / l. Serious unexpected bleeding (for example, gastrointestinal) or hemorrhagic stroke occurs when thrombocytopenia is less than 10 x 109 / l. Etiology and pathogenesis

• • Thrombocytopenia can occur as a manifestation of drug allergy (allergic thrombocytopenia), due to the production of antiplatelet antibodies (autoimmune thrombocytopenia), caused by infections, intoxications, thyrotoxicosis (symptomatic).
  • In newborns, thrombocytopenia can be caused by the passage of autoantibodies from the sick mother through the placenta (transimmune thrombocytopenia).
  • Pathology of thrombopoiesis
  • The maturation of megakaryocytes is selectively destroyed by thiazide diuretics and other products especially used in chemotherapy, ethanol
  • A special root cause of thrombocytopenia is ineffective thrombopoiesis associated with the megaloblastic type of hematopoiesis (occurs with a lack of vitamin B|2 and folic acid, as well as with myelodysplastic and preleukemic syndromes). In the bone marrow, morphologically and functionally abnormal (megaloblastic or dysplastic) megakaryocytes are detected, giving rise to a pool of defective platelets that are destroyed in the bone marrow
  • Amegakaryocytic thrombocytopenia is a rare underlying cause of thrombocytopenia due to a congenital deficiency of megakaryocytic colony-forming units.
  • Anomalies in the formation of the platelet pool appear when platelets are eliminated from the bloodstream, the most common cause is deposition in the spleen
  • Under normal conditions, the spleen contains 30% of the platelet pool.
  • The development of splenomegaly is accompanied by the deposition of a larger number of cells with their exclusion from the hemostasis system. With extremely large spleen volumes, 90% of the total platelet pool is likely to be deposited
  • The remaining 10% in the peripheral circulation has a normal duration of circulation.
  • Increased platelet destruction in the periphery is the most common form of thrombocytopenia; such conditions are characterized by a shortened platelet life span and an increased number of bone marrow megakaryocytes. These disorders are referred to as immune or non-immune thrombocytopenic purpura.
  • Immune thrombocytopenic purpura
  • Idiopathic thrombocytopenic purpura (ITP) is a prototype of thrombocytopenia caused by immune mechanisms (there are no obvious external causes of platelet deformity). See Idiopathic Thrombocytopenic Purpura.
  • Other autoimmune thrombocytopenia due to the synthesis of antiplatelet antibodies: post-transfusion thrombocytopenia (associated with exposure to isoantibodies), therapeutic thrombocytopenia (for example, stimulated by quinidine), thrombocytopenia due to sepsis (the incidence can reach 70%), thrombocytopenia in combination with SLE and others autoimmune diseases. Treatment is focused on correcting the underlying pathology. It is necessary to stop taking all potentially dangerous medicinal products. Glucocorticoid therapy is of questionable value, except for thrombocytopenia in SLE. Transfused platelets undergo the same accelerated destruction.
  • Non-immune thrombocytopenic purpura
  • Infections (for example, viral or malaria)
  • Massive transfusion of preserved blood with a low platelet count
  • ICE
  • Prosthetic heart valves
  • Thrombotic thrombocytopenic purpura. Genetic Aspects
  • Thrombocytopenia (*188000, R). Clinically: macrothrombocytopenia, hemorrhagic diathesis, rib aplasia, hydronephrosis, recurrent hematuria. Laboratory: autoantibodies to platelets, shortening of platelet life, increased clotting time, turnstile test is normal, damage to the plasma component of hemostasis.
  • May-Hegglin anomaly (Hegglin’s syndrome, 155100, R). Macrothrombocytopenia, basophilic inclusions in neutrophils and eosinophils (Dele bodies).
  • Epstein syndrome (153650, R). Macrothrombocytopenia in combination with Allport’s syndrome.
  • Fechtner family syndrome (153640, R). Macrothrombocytopenia, inclusions in leukocytes, nephritis, deafness.
  • Congenital thrombocytopenia (600588, Ilq23.3-qter deletion, R). Clinically: congenital dysmegakaryocytic thrombocytopenia, non-cardinally pronounced hemorrhagic syndrome. Laboratory: deletion of Ilq23.3-qter, increase in the number of megakaryocytes, giant granules in peripheral blood platelets.
  • Thrombocytopenia cyclic (188020, R). Hemorrhagic diathesis, cyclic neutropenia.
  • Thrombocytopenia Paris-Troussde (188025, deletion of Ilq23, defect in the TCPT gene, R). Clinically: hemorrhagic diathesis, thrombocytopenia, hypertelorism, ear anomalies, mental retardation, aortic coarctation, developmental delay in the embryonic period, hepatomegaly, syndactyly. Laboratory: giant granules in platelets, megakaryocytosis, micromegakaryocytes.
  • Bernard-Soulier syndrome (giant platelet syndrome,
  • 231200, three types of gene damage) – congenital thrombocytopathy, hemorrhages in the skin, mucous membranes, internal organs, nosebleeds; thrombocytopenia, giant (lymphocyte-like) platelets, clotting time is increased; three forms are distinguished: mild, severe (blood transfusion is required) and lethal; platelets lack glycoprotein 1b, which is responsible for the interaction between the von Willebrand factor and the platelet membrane, which leads to impaired platelet adhesion to collagen
  • Type A (231200, 17pter-pl2, GP1BA gene defect [platelet glycoprotein Ib-a], p)
  • Type B (138720, 22qll.2, gene defect GP1BB[GP9,
  • 173515, platelet glycoprotein IX], polygenic inheritance)
  • Type C (173515, chr.3, defective GP9 gene [platelet glycoprotein IX]).
  • Gray platelet syndrome (deficiency of a-granules, 139090,R). Clinically: an increase in the size of platelets, a gray color. Dabo; ratorno: a decrease in the number of a-granules and platelet-specific proteins of a-granules.

The clinical picture is determined by the underlying disease that caused thrombocytopenia.

Diagnostics

• • Thrombocytopenia is an indication for bone marrow examination for the presence of megakaryocytes, their absence indicates a violation of thrombocytopoiesis, and their presence indicates either peripheral destruction of platelets, or (in the presence of splenomegaly) platelet deposition in the spleen
  • Pathology of thrombopoiesis. The diagnosis is confirmed by detection of megakaryocytic dysplasia in a bone marrow smear.
  • Anomalies in the formation of the platelet pool. The diagnosis of hypersplenism is made with moderate thrombocytopenia, a normal number of megakaryocytes in a bone marrow smear, and a significant increase in the spleen
  • Diagnosis of idiopathic thrombocytopenic purpura requires the exclusion of diseases that occur with thrombocytopenia (for example, SLE) and thrombocytopenia caused by medication (for example, quinidine). Known available, but non-specific methods for the detection of antiplatelet AT.

Treatment:

• • Pathology of thrombopoiesis. Treatment is based on elimination of the damaging agent, if likely, or treatment of the underlying disease; platelet half-life is traditionally normal, allowing platelet transfusions to be performed in the presence of thrombocytopenia and signs of bleeding. Thrombocytopenia, caused by a lack of vitamin B12 or folic acid, disappears with the restoration of their normal level.
  • Amegakaryocytic Thrombocytopenia responds well to therapy, traditionally prescribe antithymocyte Ig and cyclosporine.
  • Anomalies in the formation of the platelet pool. Traditionally, there is no treatment, although splenectomy may resolve the problem. During transfusions, some of the platelets are deposited, which makes transfusions less effective than in states of reduced bone marrow activity.

Treatment of idiopathic thrombocytopenic purpura – see. Purpura idiopathic thrombocytopenic.

Complications and related conditions

• • Reduced platelet production is associated with aplastic anemia, myelophthisis (replacement of the bone marrow by tumor cells or fibrous tissue), and some rare congenital syndromes
  • Evans syndrome (Fischer-Evans syndrome) is a combination of autoimmune hemolytic anemia and autoimmune thrombocytopenia.

See also Von Wichlebrand disease, Idiopathic thrombocytopenic purpura, Thrombotic thrombocytopenic purpura, Thrombocytopathy

ICD

• • D69 Purpura and other hemorrhagic conditions
  • M31.1 Thrombotic thrombocytopenic purpura
  • D69.0 Allergic purpura
  • D69.1 Qualitative platelet damage, Bernard-Soulier (giant platelet) syndrome, Glanzmann disease, gray platelet syndrome, thrombasthenia (hemorrhagic) (hereditary), thrombocytopathy
  • D69.3 Idiopathic thrombocytopenic purpura, Evans syndrome
  •  D69.4 Other primary thrombocytopenias, transient neonatal thrombocytopenia (P61.0), Wiskott-Aldrich syndrome (D82.0)
  • D69.5 Secondary thrombocytopenia
  • D69.6 Thrombocytopenia, unspecified MS
  • 139090 Gray platelet syndrome
  • 153640 Vochtner Family Syndrome
  • 153650 Epstein’s syndrome
  • 155100 May-Högglin Anomaly
  • 188000 Thrombocytopenia
  • 188020 Thrombocytopenia cyclic
  • 188025 Thrombocytopenia Paris-Trussb
  • 231200 Bernard-Soulier syndrome
  • 600588 Thrombocytopenia, congenital

Literature. Bernard J, Soulier JP: Sur une nouvelle variete de dystrophie thrombocytaire-hemoragipare congenitale. Sem. Hop. Paris 24: 3217-3223, 1948; Budarf ML et al: Identification of a patient with Bernard-Soulier syndrome and a deletion in the DiGeorge/velo-cardio-facial chromosomal region in 22qll.2. Hum. Molec. Genet. 4: 763-766, 1995; Favier R et al: A novel genetic thrombocytopenia (Paris-Trousseau) associated with platelet inclusions, dysmegakaryopoiesis and chromosome deletion at II23. C. R. Acad. sci. 316: 698-701, 1993