Symmetrical onychomadesis (also know as idiopathic onychomadesis or lupoid onychodystrophy) is a clinical syndrome of unknown cause, characterized by sudden onset of painful symmetrical lesions limited to the nails. The nails become soft and deformed and often slough. The disease can occur in any breed of dog but previous studies have found that German shepherds may be predisposed, suggesting a genetic etiology. A similar syndrome is described in Norwegian Gordon setters and English setters. Dogs had sudden onset of symmetrical onychomadesis that affected multiple claws. The age of onset was between 2 and 7 years of age. Interestingly, in this series of 22 dogs, 7 owners reported first noticing nail lesions during hunting season. The histologic findings were similar to what has been previously reported: interface dermatitis and a lymphocytic plasmacytic infiltrate. Six of the affected dogs had siblings with the disease. All but 1 dog was treated with essential fatty acid supplementation. Analgesics were administered as needed. Half of the dogs were treated with oral tetracycline and niacinamide and/or prednisone. Complete remission with regrowth of normal nails occurred in only 2 of the 22 dogs. Eleven dogs had soft, abnormal nails but no pain, and 6 dogs had intermittent painful relapses. Three dogs were euthanized.
COMMENTARY: The cause of this disease is unknown. To date, there has been no clear association with vaccination, allergic disease, metabolic disease, or mineral deficiency. The high prevalence in German shepherds as well as Norwegian Gordon setters and English setters may suggest a genetic predisposition; however, the trigger of the disease remains unknown. The disease can be treated, but treatment outcomes vary from complete resolution to chronic relapsing episodes.
Symmetrical onychomadesis in Norwegian Gordon and English setters. Ziener M, Bettenay SV, Mueller RS. VET DERMATOL 19:88-94, 2008.