Fibroadipose Hyperplasia or Overgrowth (FH/FAO) is one of the PIK3CA-related overgrowth syndromes (PROS).

Chromosome: 3q26.32

Gene: PIK3CA (phosphoinositide-3 kinase)

Genetic alteration: somatic mutation with postzygotic mosaic gain-of-function


Inheritance: not known to be inherited


Clinical features:

(1) segmental progressive overgrowth of subcutaneous and visceral fibroadipose tissue

(2) skeletal overgrowth

(3) disproportionate linear overgrowth

(4) vascular malformation

(5) epidermal nevi

(6) polydactyly

(7) lipomatous infiltration of muscle

(8) testicular or epididymal cysts, hydrocele

(9) visceral overgrowth excluding spleen and thymus

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