[Neonatal thrombocyte values in children with Down's syndrome and other autosome trisomies].

Platelet counts were determined in 70 neonates with trisomy-21, 10 neonates with trisomy-18 and 6 neonates with trisomy-13 during the first days of life. 60% of all infants with trisomy-aberrations were found to have thrombocytopenia. Platelet counts in Down's syndrome averaged 104600 (SD 53000; median 90500; 10- and 90-percentile at 45000 and 175000) per microliter. A correlation with other hematological features of trisomy-21 was examined. There was no significant correlation between platelet counts and hemoglobin concentration. Similarly the difference in platelet counts between trisomy-neonates with and without polycythemia was statistically not significant. In contrast, 27 normal neonates with polycythemia showed significantly higher platelet counts (mean = 13400) than their trisomy-counterparts (mean = 98900; P = 0.01). In addition, there was no correlation, in trisomy infants, between either erythroblastosis or low birth weight and platelet count. These findings point to defective hematopoiesis as a primary cause of thrombocytopenia in trisomy-infants.