- Congenital extra-digit
- Extra-digit located more often on feet
- Bone palpable within extra-digit
- Digit may have voluntary movement
- Supernumerary Digit (no bony attachment)
- Carpenter's Syndrome
- Ellis-Van Creveld Syndrome
- Meckel-Gruber Syndrome
- Trisomy 13
- Orofaciodigital Syndrome
- Rubinstein-Taybi Syndrome
- Amputation of digit at age > 1 year
- Behrman (2000) Nelson Pediatrics, Saunders, p. 2093
- Fuloria (2002) Am Fam Physician 65(2):265-70 [PubMed]