Macrodactyly, or digital gigantism, is an extremely rare, nonhereditary, congenital deformity characterized by hyperplasia of one or more digits.1,2 In genuine cases, all physical structures of the affected digit are enlarged.3 The etiology of macrodactyly is not completely clear; it may be related to a neurogenic disorder or due to tumorous overgrowth of a single tissue type in the affected digit.3,4 Individuals with moderate-to-severe macrodactyly may experience pain and reduced range of motion (ROM), which often impairs hand function. Although ongoing observation may be adequate for mild cases with few functional limitations, surgery – including soft tissue debulking, epiphysiodesis, osteotomy, ostectomy, and ray amputation – is often needed for more severe cases.1,2,5
Pathophysiology
- Proposed mechanisms include:
- Association with a neurogenic disorder, constituting a component of neurofibromatosis3
- Disturbance of the growth-limiting factor during development, resulting in a local increase in size3
- Tumorous overgrowth of a single element of tissue in the digit, as in hemangioma, lymphangioma, or enchondroma4
- Lipomatous degeneration and disturbance of fetal circulation and local growth promoting/inhibiting factors4
- Several classification systems have been used to describe macrodactyly
- True macrodactyly and pseudomacrodactyly7
- Hamartomatous enlargement of all mesenchymal elements of the fingers (phalanges, tendons, nerves, blood vessels, subcutaneous fat, fingernails, skin coverings), but the adjoining metacarpals are not typically affected3
- True macrodactyly has been further classified as static or progressive
- Static: present at birth, and the marked overgrowth enlarges proportionally throughout development
- Progressive: not as noticeable at birth, but the marked overgrowth enlarges disproportionally faster than the rest of the limb throughout development8
- Another classification system proposes four types of macrodactyly
- Type I: comorbid lipofibromatosis of a nerve, and static or progressive subtype
- Type II: associated with neurofibromatosis
- Type III: associated with hyperostosis
- Type IV: associated with hemihypertrophy9
Related Anatomy
- Macrodactyly encompasses a variety of clinical phenotypes, with the rate, location, and extent of overgrowth differing greatly among patients2
- One or more digits may be involved, and the affected digits are always adjacent6
- The index finger is most commonly affected, followed by the long finger, thumb, ring finger, and little finger3
Incidence and Related Conditions
- Macrodactyly of the hands accounts for ~0.9% of all upper extremity congenital anomalies; it is less common in the feet11
- Macrodactyly is slightly more common in males than in females (7:5)8
- Macrodactyly is associated with other syndromes, including proteus, carpal tunnel, Bannayan– Riley–Ruvalcaba, Maffucci, and Klippel–Trenaunay–Weber
- Macrodactyly is associated with other dactylys, including syndactyly, polydactyly, and clinodactyly
- Macrodactyly simplex congenita or macromelia
- Hemihypertrophy
- Neurofibromatosis or lipofibromatous hamartoma of the median nerve
- Milroy’s disease or Ollier’s disease
- Adrenal carcinoma, hepatoblastoma, or Wilm's tumor
Differential Diagnosis
- Proteus syndrome
- Arteriovenous malformation (AVM)
- Congenital lymphangioma
- Macrodystophia lypomatosa progressive
Exam Findings, Signs and Positive Tests
- Diagnosis of macrodactyly is based primarily on a physical examination and patient history in most cases
- Physical exam should consist of palpation and inspection for thick and fatty tissue of the involved digit, as well as impaired ROM and/or instability
- If macrodactyly is encountered during a fetal scan, a thorough evaluation of all systems with special attention to soft tissues and serial scans for development of additional findings such as hemihypertrophy or signs of fetal hydrops is recommended
- A detailed family history and examination of family members may also help to diagnose an autosomal dominant syndrome associated with macrodactyly if one is present4