Bloom Syndrome Presenting With Early-Onset Myelodysplastic Syndrome and Triple Overlapping Vascular Neurocutaneous Phenotypes: A Case Report.

Bloom syndrome is a rare autosomal recessive chromosomal instability disorder characterized by growth deficiency and early-onset malignancies, and its coexistence with multiple vascular neurocutaneous syndromes is exceptionally uncommon. We report an 8-year-old girl who presented with severe growth failure and persistent pancytopenia. Bone marrow examination showed hypocellularity with monosomy 7, consistent with myelodysplastic neoplasm, and molecular analysis identified a homozygous pathogenic BLM variant (NM_000057.4:c.796C>T; p.Arg266Ter). Clinically, she exhibited overlapping neurocutaneous features within the spectrum of Sturge-Weber syndrome, Klippel-Trénaunay syndrome, and phakomatosis pigmentovascularis. The course was complicated by severe sepsis, leading to death before hematopoietic stem cell transplantation could be performed. This case highlights the importance of considering inherited cancer predisposition syndromes in children with cytopenia, growth failure, and complex neurocutaneous phenotypes.