A 33-year-old African-American man is referred to dermatology—somewhat reluctantly—by his primary care provider for evaluation. A “fungal infection” has affected his fingernail on and off for several years, persisting despite four months of terbinafine treatment (250 mg/d).
The patient denies any antecedent trauma to the finger. He does have a history of hand eczema, mostly affecting the palmar surface of his hand, and atopy, marked by seasonal allergies and sensitive skin.
EXAMINATION
The patient’s fourth fingernail on his right hand is significantly dystrophic, with transverse ridges and modest onychorrhexis. The cuticle is detached from the nail plate, but the distal nail plate appears normal.
There are signs of his dyshidrotic hand eczema, with several 2 to 3 mm intradermal vesicles in the distal palm. Some spill onto the sides of his fingers.
What is the diagnosis?