To the best of our knowledge, there are three patients previously described with isolated upper limb muscle overgrowth and with a confirmed PIK3CA mutation.7, 8 In 2014, Castiglioni et al reported the first mosaic PIK3CA mutation in a patient with unilateral isolated muscular hypertrophy of the left hand and arm and aberrant muscles. The gene discussed is PIK3CA; the disease is Skeletal muscle hypertrophy.