Definition
- Rare progressive overgrowth disorder that is asymmetric, disproportionate and mosaic
Aetiology
- Somatic activating AKT1 mutation, present only in affected tissues
- Sporadic, not inherited
Clinical Features
- Diagnosis rests on worsening of existing features and appearance of new ones
- Normal at birth, with overgrowth starting in early childhood
- Cerebriform connective tissue naevus of the sole is close to pathognomonic
- Macrodactyly
- Hemihypertrophy and limb length discrepancy
- Skin thickening
- Lipomas and subcutaneous tumours
- Linear verrucous epidermal naevus
- Vascular malformations
- Skull hyperostosis and macrocephaly
- Scoliosis and enlarged vertebral bodies
Differential Diagnosis
- Klippel-Trenaunay syndrome
- CLOVES and other PIK3CA related overgrowth
- Neurofibromatosis type 1
- Isolated hemihyperplasia
Management
- Multidisciplinary care with serial review of growth
- Epiphysiodesis for limb length discrepancy, timed with caution as growth is unpredictable
- Debulking or ray amputation for macrodactyly
- Bracing or fusion for scoliosis
- Corrective osteotomy for angular deformity
Complications
- Deep vein thrombosis and pulmonary embolism, a leading cause of death
- Perioperative thromboprophylaxis is advised
- Recurrence of overgrowth after surgery
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.