Clinical pitfalls: a painful nail enlargement

Editor Alterations in the structure and appearance of the nail unit may be seen in association with a variety of dermatological disorders. 1 Because of the limited number of reaction patterns associated with the nail unit, many of the changes that are seen, such as onycholysis, pitting and subungual hyperkeratosis, are not specific. However, certain clinical findings, especially when present in combination, may be highly suggestive of a specific diagnosis or may assist in limiting the differential diagnosis. A 63-year-old woman was referred for the evaluation of a painful enlargement and severe third left finger nail deformity of 2 months' duration. The lesion started at the dorsal side of the proximal nail fold and migrated distally toward the hyponychium. Clinically, there was a greenish-blue discoloration associated to severe onychodystrophy, massive subungual hyperkeratosis causing uplifting of the nail plate and partially onycholysis at the distal phalanx (fig. 1). The woman was otherwise in good general health, and there was no involvement of other skin areas. A fungal infection of the area was excluded by examination of a potassium hydroxide preparation. Complete general physical and mucocutaneous examination was done. Laboratory evaluation was within normal limits. The patient refused the nail biopsy. The risk of scarring and injuring the nail matrix was unacceptable to her. Ultrasonography (US; fig. 2) with very high frequency transducers (Esaote AU-4 Idea Biomedica, Genoa, Italy) of the distal interphalangeal joint showed well-defined thickness of the nail matrix and nail bed. Hand X-ray film revealed acral lamellar periostitis; both were suggestive of the diagnosis of nail psoriasis. Keratolytic agents and topical Calcipotriol/betamethasone dipropionate were administered. After 2 weeks of treatment, there was a clear improvement confirming the clinical and imaging diagnosis. Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2·5, which does not permit commercial exploitation. fig. 1 Advanced subungual hyperkeratosis resulting in uplifting of the nail plate with distal nail bed, 'oil spot' involvement of nearly the entire nail bed and hyponychial involvement. fig. 2 Real-time US using 13-MHZ linear probe; sonographic longitudinal section of the distal interphalangeal joint showed well-defined thickness of the nail matrix and nail bed, with slight eye catching signal at power Dop-pler, together with superficial soft tissue thickening at the distal phalanx.