Which clinical feature is indicative of a subcutaneous infection due to sporotrichosis?

The clinical feature indicative of a subcutaneous infection due to sporotrichosis is nodules on the forearms. Sporotrichosis, caused by the fungus Sporothrix schenckii, commonly presents as subcutaneous nodules, particularly in areas of trauma or where the fungal spores typically enter the body, such as the hands or forearms.

Infection often begins as a small, painless bump that can develop into larger nodules that are ulcerative in nature. The lesions can be seen closely following the path along lymphatic drainage, leading to a linear track of nodules. Given that occupational exposure (like gardening or handling plant material) is a common risk factor, forearms are often the site where these nodules develop.

The other clinical features do not accurately reflect the typical presentation of sporotrichosis. Extensive necrosis would more likely suggest a severe, necrotizing infection or a different microbial etiology. A pruritic rash is generally more indicative of allergic reactions or other fungal infections, and bilateral nodules do not capture the focal nature of sporotrichosis, which tends to present unilaterally along lymphatic vessels. Thus, the most characteristic feature of sporotrichosis is indeed the presence of nodules