Multiple calcified subungual epidermoid inclusions.J Am Acad Dermatol 2007; 56(2):336-9JA
Subungual epidermoid inclusions (also known as subungual onycholemmal cysts) are an uncommon and distinctive nail abnormality occurring in the dermis of the nail bed. Clinically the nail plate may exhibit onychodystrophy, clubbing, ridging, thickening, pigmentation, or appear normal. We report the case of a patient with onychodystrophy of the right halux of 7 years' duration. This case is presented with serial pictures demonstrating the gradual development of nail plate thickening, yellow discoloration, and nail bed hyperkeratosis indicative of the disease. She had negative fungal cultures, poor response to topical and oral antifungal agents, and an initial nondiagnostic superficial biopsy. Repeat full-thickness nail bed biopsy results revealed multiple calcified subungual epidermoid inclusions epidermoid inclusions. Histologic features included characteristic elongation of the rete ridges with cyst formation and pinching off of the connection to the nail bed epithelium, forming free-lying cysts within the dermis of the nail bed. The cysts contained compact onycholemmal keratin and calcification. A granular layer was not present. This case reinforces the need to clinically reassess, possibly x-ray, and perform a sufficient biopsy for persistent undiagnosed nail unit disorders. Subungual calcified inclusions may be an underrecognized and more common entity than currently recognized.