Atypical plaque on the hand

Submitted by Dr Henry Foong, Ipoh, Malaysia

An 80-year-old retired goldsmith presented with 4-month history of an ulcerated plaque on the left hand. It had gradually increased in size. His past medical history included hypertension, diabetes mellitus, and ischemic heart disease. His medications included norvasc, zocor, ticlid and amaryl.

Examination of the skin showed a localized ulcerated verrucous plaque 6 x 6 cm on the dorsum of the left hand. Closer examination showed slough and blackish dots on the surface of the plaque. Regional nodes were not enlarged.

Our presumptive diagnosis is either atypical mycobacterium infection or chromoblastomycosis.

The epithelium shows pseudoepitheliomatous hyperplasia. The upper dermis is densely infiltrated by acute and chronic inflammatory cells. Neutrophils are also noted in the lining epithelium. No granulomas or Langhan's giant cells are seen. No microorganisms are noted. Negative for dysplasia and malignancy. Ziehl-Neelsen stain for acid fast bacilli is negative. Periodic acid Schiff stain for fungi is negative. Culture for AFB and fungal organism were negative

He was initially treated with itraconazole 100mg bd and after 2 weeks there was no improvement at all. Bactrim 2 tab daily was added and this time it showed improvement after 2 weeks of the combination.

One of the differential that was considered is pustular vasculitis or neutrophilic dermatosis of the dorsum of the hands. Points supporting this diagnosis include pseudoepitheliomatous hyperplasia and the absences of granuloma on histology examination.

I suspect this could be atypical mycobacterium infection based on the empirical therapeutic response to bactrim. I wonder what your views are with regard to this case?