Necrotic Ulcer on the Thigh

The Diagnosis: Disseminated Cryptococcosis

Histopathologic examination of a 3-mm punch biopsy showed a diffuse dermal neutrophilic infiltrate with necrosis and subcutaneous tissue with round yeast surrounded by a prominent halo staining bright red with mucicarmine, representing a thick mucinous capsule (Figure). Grocott-Gomori methenamine-silver and periodic acid-Schiff stains also demonstrated fungal spores morphologically. Cerebrospinal fluid culture grew Cryptococcus neoformans, and cryptococcal antigen titers were positive in both serum and cerebrospinal fluid samples (>1:4096). The patient had autolytic debridement of the ulcer after completing a 4-week induction course of intravenous liposomal amphotericin B with oral flucytosine. He was transitioned to oral fluconazole for the consolidation phase of treatment.

Diffuse dermal neutrophilic infiltrate with necrosis and subcutaneous tissue with round yeast surrounded by a prominent halo (arrow) staining bright red with mucicarmine, representing a thick mucinous capsule (original magnification ×400).

Cryptococcus is an opportunistic basidiomycetous yeast with worldwide distribution and 2 primary pathogenic species in humans: C neoformans and Cryptococcus gattii. It is associated with bird feces, composted food, and decayed wood.^1,2 A predilection toward an immunosuppressed host is recognized in 70% to 90% of the infections caused by C neoformans; however, C gattii commonly affects individuals with apparently intact immune systems.^1,3 Risk factors for infection include advanced human immunodeficiency virus infection, solid organ transplantation, chronic liver disease, autoimmune disease, hematological malignancy, and underlying genetic susceptibility.^1,2

Initial exposure is through the respiratory tract with formation of latent reservoirs in the pulmonary lymph nodes with subsequent reactivation that can result in hematogenous dissemination.^1,2 Cutaneous involvement was described in 108 patients (5%) in a large review of 1974 cases in France.⁴ Among those with cutaneous involvement, disseminated disease was diagnosed in 80 cases (74%), and 28 cases (26%) were considered primary cutaneous cryptococcosis. Primary cutaneous cryptococcosis typically presents as a single lesion, predominantly on the hand, with whitlow and more rarely with extensive cellulitis or necrotizing fasciitis.⁴ In disseminated cutaneous disease, there is no pathognomonic single lesion; however, it is commonly associated with multiple cutaneous lesions predominantly involving the head and neck. Plaques, abscesses, nodules, and pustular or umbilicated papules have been reported.^1,5 There are few case reports that describe a single isolated necrotic ulcer with disseminated disease similar to our presented case, and more typically the necrotic ulcer is seen in transplanted patients.⁶ The differential diagnosis of a necrotic thigh ulcer includes pseudomonal ecthyma gangrenosum, cutaneous anthrax and aspergillosis, fusariosis, and a bite from the brown recluse spider.⁷ Our patient had an increased susceptibility to infection from his ongoing chemotherapy, a risk previously described in oncology patients with cell-mediated immunosuppression.⁸

Management for disseminated cryptococcosis is a 3-phase therapy including induction with intravenous amphotericin B and oral flucytosine for a minimum of 2 weeks, with consolidation and maintenance phases both with oral fluconazole for a length depending on underlying immunosuppression.⁹