Shahin Mafinezhad - Department of Pediatrics, North Khorasan University of Medical Sciences, Bojnurd, Iran
Hasan Boskabadi - Department of Pediatrics, Mashhad University of Medical Sciences(MUMS), Iran
Ghasem Bayani - Department of Pediatrics, North Khorasan University of Medical Sciences, Bojnurd, Iran
Hojatollah Ehteshammanesh - Department of Pediatrics, North Khorasan University of Medical Sciences, Bojnurd, Iran

Background: A fault in chromosome distribution during cell division leads to aneuploidy, which can be associated with thrombocytopenia. Various hematological abnormalities have been reported among neonates with Down syndrome (DS). Neutrophilia, thrombocytopenia and polycythemia were the most common hematological abnormalities observed among neonates with Down syndrome. In particular, thrombocytopenia below 150×109/L was approximately two-third (66%) of DS and 6% of counts <50,000/microl was detected during the 1st week of life. The exact mechanism remains unknown, but is thought to be due to decreased platelet production from chronic fetal hypoxia, which also leads to intrauterine growth retardation and suboptimal response of the thrombopoitin (TPO) system to thrombocytopenia in DS during the neonatal period. Few cases of alloimmune thrombocytopenia (NAIT) with DS due to anti-HPA antibody were reported.Methods: Data from multihospital healthcare systems shows large two case series of infants with cytogenetically confirmed DS and a reference group infants without birth defects all born during the period 2009-2015.During this period, 145,522 live births were recorded at 18 hospitals. Down syndrome was recognized in 226 (1 in 644). Data were analyzed using multivariate logistic regression analysis expressed as adjusted odds ratio (aORs) with 95% confidence intervals (95% CIs).Results & Conclusion: Infants with DS had a significantly higher risk for thrombocytopenia (aOR = 32.4, 95% CI: 15.2-68.9). Platelet counts in Down s syndrome averaged 104600 (SD 53000; median 90500; 10- and 90-percentile at 45000 and 175000) per microliter. The mean platelet volume did not correlate with the platelet count, but tended to run slightly large (9.2 +/- 1.3 fl). Persistence of thrombocytopenia beyond 8 to 12 weeks after birth should warrant a hematology consult. Thrombocytopenia can be seen associated with some types of congenital heart defects. Karyotype testing should be done in all obviously dysmorphic infants with thrombocytopenia. Pediatricians who are involved in the care of patients with DS need to be aware of the associated bleeding tendency and other hematologic problems, as these patients will often require surgical procedures. It seems reasonable to recommend that one or more CBCs be obtained on all neonates with Down syndrome.

down syndrome, thrombocytopenia, neonate, CBC