Hyperphalangy is a congenital, non-syndromic limb malformation characterized by the presence of an accessory phalanx between metacarpal/metatarsal and proximal phalanx, or between any two other phalanges of a digit, excluding the thumb. Hypherphalangy is almost always bilateral and patients present no more than five digits and no other skeletal anomalies. The disease is Monarch Disease Ontology identifier MONDO_0017455 (hyperphalangy). Also known as: supernumerary phalanges, supernumerary phalanx.