[Tranverse acro-osteolysis: A rare cause of nail dystrophy]

Acro-osteolysis (AO) involves partial or total destruction of the distal phalanges of the fingers or toes. The range of forms of AO is extremely wide. A distinction is generally made between the acquired forms and the genetic and idiopathic forms. Herein we report a case of idiopathic transverse single-finger AO associated with onychopathy.

A 48-year-old woman consulted for a nail lesion involving brachyonychia in the right index finger alone (pseudo-clubbing appearance of the finger). The remainder of the clinical examination was normal, particularly in terms of neurological and dermatological investigations. Standard x-rays revealed transverse osteolysis of the middle third of the distal phalanx, occurring solely in the right index finger.

While certainty regarding diagnosis of AO depends upon radiological findings, the radiological appearance is not specific. Two subgroups suggesting aetiological diagnosis may be distinguished: transverse AO with banding and longitudinal AO. With transverse AO, the diaphysis of the distal phalanx presents osteolysis with banding, but with sparing of the base of the band (pseudo-fracture appearance); this appearance is suggestive of toxic causes, congenital familial conditions or repetitive micro-trauma. Upon x-ray examination, the longitudinal forms exhibit concentric resorption of the band and these forms are more often seen in a setting of neurological, vascular or metabolic disorders. The associated nail involvement frequently present helps clarify the diagnosis, with nail plate shape being dependent on the integrity of the underlying bone.

Herein we report the first case of transverse AO in a single finger associated with brachyonychia, and with no discernible cause.