= rare nonhereditary congenital form of localized gigantism = neural fibrolipoma with macrodactyly

Path: striking increase in adipose tissue in a fine fibrous network involving periosteum, bone marrow, nerve sheath, muscle, subcutaneous tissue

May be associated with: syn-, clino-, polydactyly

• painless

Location: 2^nd or 3^rd digit of hand / foot; unilateral; one / few adjacent digits may be involved in the distribution of the median / plantar nerves

• long + broad splayed phalanges with endosteal + periosteal bone deposition
• overgrowth of soft tissue, greatest at volar + distal aspects
• slanting of articular surfaces
• lucent areas of fat (DIAGNOSTIC)

Prognosis: accelerated maturation possible; growth stops at puberty

DDx: fibrolipomatous hamartoma associated with macrodystrophia lipomatosa (indistinguishable), Klippel-Trénaunay-Weber syndrome, lymphangiomatosis, hemangiomatosis, neurofibromatosis, chronic vascular stimulation, Proteus syndrome