A puzzling diagnosis: mycosis fungoides masquerading as pyoderma gangrenosum

Abstract

<p class="abstract">Mycosis fungoides (MF) is a form of cutaneous T cell lymphoma that initially affects the epidermis, and is characterized by the clonal proliferation of mature cluster of differentiation (CD4)+T cells. We report a 73-year old male presenting with chin and right axillary skin lesions that had ulceration and granulating areas. Initial biopsy revealed mixed inflammatory cell infiltrate, which suggested an initial diagnosis of pyoderma gangrenosum. Despite treatment, the progressive worsening of the skin lesions prompted multiple repeat biopsies, which eventually revealed a predominance of T cells within the infiltrate. A T cell receptor rearrangement resulted in elevated monoclonal T cell populations, confirming a diagnosis of MF. Subsequent positron emission tomography (PET) scans revealed metastatic involvement of the disease, which ultimately led to the patient’s death. Clinical presentations of MF can mimic several different clinical entities, including pyoderma gangrenosum. This report highlights the importance of a multimodal approach to the diagnosis of unidentified skin lesions.</p>