Which of the following conditions is characterized by painless, proximally expanding pigmentation in the nail?

• A. Subungual melanoma
• B. Acral lentiginous melanoma
• C. Chronic onychomycosis
• D. Dermatofibroma

Answer: (A)

The condition characterized by painless, proximally expanding pigmentation in the nail is subungual melanoma. This type of melanoma often presents as a dark streak or band under the nail and can spread progressively towards the cuticle. The absence of pain during its early stages distinguishes it from other pathologies that may present with nail changes but typically involve discomfort or other symptoms.

Subungual melanoma is associated with the presence of pigment, which may appear as a longitudinal dark stripe. As it progresses, the pigmentation may become broader and more irregular, leading to a visible change in the nail. Early recognition is crucial for better treatment outcomes since nail pigmentation that changes atypically can often be indicative of underlying malignancy.

In contrast, acral lentiginous melanoma predominantly occurs on the palms and soles and may not exclusively present under the nail. Chronic onychomycosis generally causes changes in nail appearance associated with fungal infection, often milky or yellow discoloration, and may cause pain or discomfort as well as thickening of the nail. Dermatofibroma refers to a benign skin tumor and does not typically cause changes in the nail structure or coloration.

Understanding these distinctions helps in recognizing subungual melanoma early, which is vital for effective management and treatment.