Enlarging Ulcerated Plaques on Bilateral Arms of a 64-Year-Old Man - QUIZ

Figure 1. Large confluent erythematous plaques with focal ulcers and scaling.

Figure 2. Several floret-like morula organisms in the dermis (hematoxylin-eosin stain, magnification x 400).

A 64-year-old retired farmer presented with a 3-month history of enlarging plaques of both upper limbs associated with several focal ulcers. Recent treatment with empirical oral and topical antibiotics had been ineffective. Apart from regular gardening, he denied contact with animals or use of nonprescribed topical agents, and had no history of malignancy.

Physical examination was notable for large nontender erythematous scaly plaques covering almost the entire forearms and upper arms with several healing ulcers (Figure 1). 

Histological examination of the skin biopsy is shown in Figure 2.

What is your diagnosis?

Clinical Infectious Diseases 2013;56(2):271.