Congenital amegakaryocytic thrombocytopenic purpura is a rare disorder characterized by isolated, moderate to severe thrombocytopenia in the first year of life in the absence of other physical abnormalities. Platelet count at the time of diagnosis ranges from 0-80,000/cmm. The bone marrow examination reveal absent or extremely scarce and small megakaryocytes with normal marrow cellularity. Alter et al (56) reported 21 cases, out of which 12 presented in first week of life and the remainder in the first 9 years. Male to female ratio was 2:3 suggestive of x-linked transmission in some cases. Half of the patients initially diagnosed as congenital amegakaryocytic thrombocytopenia eventually develop aplastic anemia at a median age of 3-5 years.

Chromosomal analysis have been normal (76). Elevated fetal Hb and i antigen also have been reported in some cases (70, 74).

Mortality from this disorder is high, usually because of hemorrhage or infection. Some patients also develop leukemia or preleukemia or pancytopenia, which develop between 5 months and 12 years of age (56).

Pathophysiology has been studied recently and Muraoka and Co-workers (79) found that serum thrombopoietin (TPO) level increased significantly higher than normal controls but response of bone marrow progenitors in vitro was defective. They did not detect expression of the TPO receptors mRNA in the marrow mononuclear cells, suggesting the defect responsible for thrombocytopenia might be an impaired expression of the TPO receptors. Guinan et al's(64) in vitro studies demonstrated IL3, GM-CSF or combination of both increased the number of CFU-MK derived colonies and IL3 administration resulted in improved platelet count and decreased bleeding and transfusion requirement.

Bone marrow transplantation has been curative in some patients. A megakaryocytic thrombocytopenia with microcephaly is a rare condition. However, to be differentiate it from congenital rubella syndrome, thrombocytopenia in this condition persists beyond 1 year of life and is not associated with other anomalies.