Activating PIK3CA somatic mutation in congenital unilateral isolated muscle overgrowth of the upper extremity.

Congenital unilateral overgrowth of the upper extremity affecting only the muscle tissue is rare. We describe on the clinical, histopathological, and neuroimaging findings in a 6-year-old girl with a congenital, non-progressive muscle enlargement of the entire left upper limb with an ipsilateral hand deformity. No cutaneous stigmata or additional features were detected. Sanger sequencing for the AKT1, PIK3CA, and PTEN genes identified an activating c.3140A>G, p.H1047R mutation in the PIK3CA gene from the affected muscle DNA. We demonstrate that isolated congenital muscular upper limb overgrowth with aberrant hand muscles is another condition related genetically to the PIK3CA-related overgrowth spectrum.