Focal gigantism

Core idea

Differentiate by:
- Tissue type overgrown: osseous, soft tissue, or both
- Presence of cutaneous manifestations
All entities with cutaneous change (may) have overgrowth of both osseous and soft tissue components.

Summary table

Condition	Overgrowth Type	Cutaneous Change?	Key Imaging/Clinical Features
Soft tissue hemangioma	Bone & soft tissue	Yes	Phleboliths, skin stain/veins, cutaneous hemangiomas
Neurofibromatosis type I	Bone & soft tissue	Yes	Café au lait, plexiform neurofibromas, tibial bowing
Klippel-Trénaunay Syndrome	Bone & soft tissue	Yes	Port wine stain, varicosities, venous/lymphatic malformation
Epidermal nevus syndrome	Bone & soft tissue	Yes	Verrucous nevi, CNS signs
Arteriovenous malformation (MSK)	Bone & soft tissue	No	Phleboliths, fast flow, no skin stain
Maffucci syndrome	Bone & soft tissue	No	Enchondromas + soft tissue hemangiomas, phleboliths
Macrodystrophia lipomatosa	Bone & soft tissue	No	Fibrofatty overgrowth, nerve territory, digits
Proteus syndrome	Bone & soft tissue	No	Mosaic overgrowth, skull/facial/chest deformity, lymphangiomas
Ollier disease	Bone only	No	Multiple enchondromas, asymmetric, hands/feet
Hyperemia (JIA, hemophilic arthropathy, chronic osteomyelits,post-trauma)	Bone only	No	Osseous hypertrophy at affected joint, young age
Lymphangioma (lymphatic malformation)	Soft tissue only	Sometimes	Cystic, non-enhancing, common in neck/axilla

Hyperemia (prior to skeletal maturation)

Juvenile idiopathic arthritis (JIA)
- Mainly around knee and elbow (large joints)
Hemophilic arthropathy
- Hemarthrosis → hyperemia → osseous overgrowth
- Affects:
  - Knee (femoral condyle)
  - Elbow (radial head)
  - Ankle (distal tibia)
Infection
- Chronic osteomyelitis
- Tuberculosis
Post-traumatic (fracture)

Pearls

JIA & Hemophilic Arthropathy:
- Imaging findings can be similar: ballooned epiphyses, widened intercondylar notch
Phleboliths: suggest vascular lesions (hemangioma, AVM, Maffucci syndrome)
Digits involved → Think Macrodystrophia lipomatosa or enchondromatosis (Ollier/Maffucci)