To report a case of a unilateral moyamoya angiopathy in an individual with a distal 16p11.2 (BP2-BP3) microdeletion. 

Moyamoya angiopathy is a rare, progressive steno-occlusive cerebral arteriopathy that is classified as either idiopathic moyamoya disease (MMD) or moyamoya syndrome (MMS). MMS is associated with genetic syndromes and well-established risk factors such as Down syndrome, neurofibromatosis type 1, sickle cell disease, or prior cranial radiation. 16p11.2 deletions are classified as either proximal (BP4-BP5) or distal (BP2-BP3) and confer vulnerability to neurodevelopmental disorders and obesity. Within the distal deletion is the RABEP2 gene, which modulates VEGFR2 signaling and endothelial cell functioning. Also included is SH2B1, which is associated with accelerated metabolic disease. Furthermore, rodent data suggest the 16p11.2 deletion negatively impacts endothelial functioning and cerebrovascular reactivity. Moyamoya angiopathy has been previously reported in one individual with a proximal 16p11.2 deletion.

We report a case of a 25 year old biological female with poorly controlled type 1 diabetes, obesity, and depression, who presented to the neurology clinic for evaluation of sensory complaints. 

MRI showed chronic gliotic changes in the right hemisphere. Conventional angiography identified right internal carotid artery occlusion with lenticulostriate collateral formation consistent with moyamoya angiopathy. There were no other signs of vasculitis or atherosclerosis. The patient underwent a successful encephaloduroarteriosynangiosis. Whole-genome sequencing revealed a distal 16p11.2 deletion (GRCh38; chr16:28812691-29034293).

Distal 16p11.2 deletions may plausibly contribute to moyamoya angiopathy through effects on endothelial permeability and vascular reactivity. However, population-based studies as well as in-human studies evaluating vascular physiology are needed to support a direct relationship.