Various chromosomal disorders present with neonatal thrombocytopenia in addition to characteristic physical features of he syndrome. Commonest syndromes encountered are Trisomies of chromosomes 13, 18 or 21 and infants with Turner's syndrome.

Hehlfeld et al (80) in a study of 5194 fetal blood samples (17 to 41 weeks) reported 4.7% samples (247 samples) with thrombocytopenia less than 150,000/ul, out of which 17% (43 samples) were due to chromosomal anomalies including Trisomy 13, Trisomy 18, Trisomy 21, Turner's syndrome and Triploidy. Hord and associates (82) in their study of 25 neonates with Down's syndrome reported thrombocytopenia (less than 100,000) in 28% of cases. Thrombocytopenia in these cases were mild to moderate (platelet count > 40,000/ul).

Neonatal thrombocytopenia are also associated with other genetic disorders like Wiskott-Aldrich syndrome, Noonan's syndrome, Alport's syndrome and other inherited metabolic disorders like methyl malonic acidemia, ketotic glycemia, isovaleric aciduria, holocarboxylase synthetase deficiency.

Wiskott-Aldrich syndrome (WAS) :

is an x-linked immunodeficiency characterized by eczema, recurrent infection and thrombocytopenia leading to severe bleeding tendency. Laboratory investigations in addition to thrombocytopenia reveal very small sized platelets, not in clumps in peripheral smear, and have impaired aggregation to ADP, epinephrine, ristocetin and collagen. Bone marrow examination shows normal megakaryocytes and there is impairment of cellular and humoral immunity. Prognosis is poor and children die of severe infection during first year of life (85,86). Splenectomy though improves platelet count, should be avoided in children for the fear of increased risk of overwhelming infections due to capsulated organisms and gram negative organisms like pneumococcus, H.influenza, meningococcus etc. particularly among the children below the age of 5-6 years. Bone marrow transplantation, now-a-days is considered as treatment of choice.

Bernard Soulier syndrome is a rare autosomal incompletely recessive disorder of moderate clinical severity characterized by giant platelets of nearly size of lymphocytes on peripheral smear, mild to moderate thrombocytopenia and clinical manifestation of cutaneous bleeds or bleeding tendency. Platelet adhesiveness and platelet aggregation by ristocetin is abnormal and they lack receptor site for factor VIII related antigen (63).