BI04: Lunar landscape of the leg

S. Shinhmar, D. Ravindran and R. Rabindranathnambi

Royal Derby Hospital, Derby, UK

We describe an extremely rare case of blastomycosis-like pyoderma (BLP), an uncommon condition usually found in immunosuppressed individuals. The exact pathogenesis is unknown; however, multiple microorganisms have been implicated (Cole DW, Huerta T, Tejasvi T, Lowe L. Vegetative and verrucous plaques in an immunosuppressed patient: blastomycosis-like pyoderma. JAAD Case Rep 2020; 6: 96–8). A 78-year-old woman with a background of monoclonal gammopathy of undetermined significance (MGUS) presented to the Emergency Department with a 2-day history of rigors, nausea, vomiting and a swollen left leg. Her left leg was erythematous and warm to the touch, and she subsequently developed bullae and nodules. Investigations revealed a C-reactive protein of 337 mg L^–1, white cell count of 9·52 × 10⁹ cells L^–1 and a D dimer of 2584 μg L^–1. Her skin swab grew Streptococcus dysgalactiae. A scan for deep vein thrombosis was negative. Magnetic resonance imaging of her left ankle and foot showed features of cellulitis. A decision was made to treat for bullous cellulitis and she was started on intravenous Tazocin^®. After approximately 3 weeks of antibiotics the rash became less exudative and the blisters had cleared, leaving peculiar residual areas of warty, thickened plaques and vegetative papules forming craters and small volcano-like ulcers resembling a lunar landscape. Our differential diagnoses were blastomycosis-like pyoderma, vegetative pyoderma gangrenosum and herpes simplex vegetans. Histological evaluation of skin biopsies from the left ankle, 2 weeks after antibiotic treatment, showed prominent widespread necrosis with hyperkeratosis, reactive hyperplasia and abrupt necrotic ulceration of the epidermis. Small neutrophilic abscesses were also noted. Microscopy and sensitivity of the skin biopsy showed scanty leucocytes only. These features supported the diagnosis of blastomycosis-like pyoderma. The rash improved significantly with 3 months of lymecyclin 408 mg q12h. BLP is a rare condition. Although its association with immunosuppression is well documented, we did not find any other cases in the literature associated with MGUS. Our patient initially presented as bullous cellulitis. During the resolution stage the cellulitis metamorphosed into BLP. We believe a tissue reaction and the host’s response secondary to acute infection led to BLP transformation. BLP should be considered as a differential in immunosuppressed patients who present with verrucous and vegetative plaques. Our patient improved significantly with a prolonged course of lymecycline; however, several other treatments such as retinoids, dapsone, systemic corticosteroids, intralesional steroids and surgery have been suggested (Cole et al.; Lee YS, Jung SW, Sim HS et al. Blastomycosis-like pyoderma with good response to acitretin. Ann Dermatol 2011; 23: 365–8).