A neonate with congenital amegakaryocytic thrombocytopenia associated with a chromosomal microdeletion at 21q22.11 including the gene RUNX1

We observed a neonate who had severe thrombocytopenia wherein evaluations for neonatal immune-mediated thrombocytopenia and congenital infections were negative, and the marrow findings were consistent with congenital amegakaryocytic thrombocytopenia (camt). a genomic microarray identified a microdeletion at 21q22.11 including the gene runx1. two somewhat similar cases were recently reported, but with multiple congenital anomalies that are not present in our case. we propose that a 21q22 deletion resulting in runx1 haploinsufficiency can produce a phenotype similar to camt with various associated anomalies depending on which adjacent genes are absent or disrupted.