Bone Marrow Failure as an Underrecognized Feature of KAT6A Syndrome.

KAT6A syndrome (Arboleda-Tham syndrome) is a rare disorder caused by heterozygous pathogenic variants in KAT6A, a histone acetyltransferase essential for chromatin remodeling and hematopoietic stem cell function. While neurodevelopmental features are well established, hematologic manifestations are underrecognized. We describe two pediatric patients from Canada and Korea who developed severe bone marrow failure and were successfully treated with hematopoietic stem cell transplantation. One carried an upstream truncating variant, the other a downstream frameshift; both disrupted domains critical for transcriptional regulation. The literature review revealed additional cases with cytopenias. Our findings highlight bone marrow failure as an overlooked feature of KAT6A syndrome.