3. Secondary immune mechanism
Drug-Induced Thrombocytopenia
•A number of drugs are associated
with immune thrombocytopenia as
the result of either an immune
process or a megakaryocyte injury.
4. Heparin-induced hrombocytopenia (and rarely thrombosis) is seldom seen in
pediatrics but occurs when, after exposure to heparin, the patient develops
an antibody directed against the heparin/ platelet factor IV complex.
5. Non immune Platelet Destruction
increase platelet consumption
DIC
hemolytic-uremic syndrome
thrombotic
thrombocytopenic purpura
The syndromes of DIC, hemolytic-uremic syndrome, and thrombotic
thrombocytopenic purpura share the hematologic picture of
The microangiopathic hemolytic anemia is characterized by the
presence of RBC fragments, including helmet
cells, schistocytes, spherocytes, and burr cells.
8. Combined Platelet and Fibrinogen Consumption Syndromes
Kasabach-Merritt Syndrome
Hemangioma
platelet trapping and activation of
coagulation with fibrinogen
consumption and generation of
fibrin(ogen)
9. Non immune Platelet Destruction
Sequestration
•Individuals with massive splenomegaly
develop thrombocytopenia, since the
spleen acts as a sponge for platelets
and sequesters large numbers.
•Most such patients will also have mild
leukopenia and anemia on the CBC.
Individuals who have
thrombocytopenia caused by splenic
sequestration should undergo a work-
up to diagnose the etiology of
splenomegaly, including
infectious, infiltrative, neoplastic, obstr
uctive, and hemolytic causes.
13. Fanconi anemia
Aplastic anemia not present
at birth, develops about 6
yr of age; fatal without
bone marrow transplant;
chromosomal breakage
challenge test available for
early diagnosis.
15. Refrences
1. Nelson textbook of pediatrics 19th edition,
Chapter 476.
2. Dan L. Longo, HARRISON’S Hematology and
Oncology;
3. Childhood idiopathic thrombocytopenic purpura
(itp): over 40 year of experiences; Medical
Journal of Islamic World Academy of Sciences
19:4, 151-160, 2011.
-http://www.uptodate.com/contents/clinical.4
-of-evaluation-and-manifestations
children-in-thrombocytopenia
thrombotic microangiopathy in which there is red cell destruction and a consumptive thrombocytopenia caused by platelet and fibrin deposition in the microvasculature
This acute disease usually follows an episode of acute gastroenteritis, often triggered by Escherichia coli 0157:H7. Shortly thereafter, signs and symptoms of hemolytic anemia, thrombocytopenia, and acute renal failure ensue. Sometimes neurologic symptoms are associated with these findings. E.coli 0157:H7 produces a specific toxin (verotoxin) that binds to and damages renal endothelial cells preferentially.
The association of a giant hemangioma with localized intravascular coagulation causing thrombocytopenia and hypofibrinogenemia is called the Kasabach-Merritt syndrome. In most patients the site of the hemangioma is obvious, but retroperitoneal and intra-abdominal hemangiomas may require body imaging for detection. Inside the hemangioma there is platelet trapping and activation of coagulation with fibrinogen consumption and generation of fibrin(ogen) degradation products. Arteriovenous malformation within the lesions can cause heart failure.The peripheral blood smear shows microangiopathic changes. Multiple modalities have been used to treat Kasabach-Merritt syndrome, including surgical excision , laser photocoagulation, corticosteroids in high doses, local x-ray therapy, and antiangiogenic agents such as interferon a2 . Over time most patients who present in infancy have regression of the hemangioma.
Congenital amegakaryocytic thrombocytopenia is caused by a rare defect in hematopoiesis that usually manifests within the first few days to weeks of life, when the child presents with petechiae and purpura caused by profound thrombocytopenia. Other than skin and mucous membrane findings, the physical examination is normal.
syndrome consists of thrombocytopenia that presents in early infancy with radial anomalies of variable severity from mild changes to marked limb shortening. In many such individuals there are also other skeletal abnormalities of the lower extremities.Intolerance to formula may complicate management by triggering gastrointestinal bleeding.
microcephaly, microphthalmia, epicanthal folds, dangling thumbs, site of ureteralreimplantation, congenital dislocated hips, and rocker bottom feet. (Alter BP, Young NS. The bone marrow failure syndromes.
is characterized by thrombocytopenia with tiny platelets, eczema, and recurrent infections due to immune deficiency. WAS is inherited as an X-linked disorder. The WAS protein appears to play an integral role in regulating the cytoskeletal architecture of both platelets and T lymphocytes in response to receptor-mediated cell signaling. The WAS protein is common to all cells of hematopoietic lineage. Molecular analysis of families with X-linked thrombocytopenia has shown that many members have a point mutation within the WAS gene, whereas individuals with the full manifestation of WAS have large gene deletions. Examination of the bone marrow in WAS shows the normal number of megakaryocytes, although the megakaryocytes may have bizarre morphology. Transfused platelets have a normal life span. Splenectomy often corrects the thrombocytopenia, suggesting that the platelets formed in WAS have accelerated destruction. About 5% of WAS patients develop lymphoreticular malignancies. Successful bone marrow transplantation cures WAS.
