LAUSR

Cutaneous mucinosis is an umbrella term for a group of heterogeneous disorders caused by abnormal accumulation of mucin, either localized to the skin or associated with systemic involvement. Mucin is a normal component of the extracellular matrix, consisting mainly of glycosaminoglycans, and is important for dermal salt and water homeostasis. We describe an unusual case of localized cutaneous mucinosis that does not appear to fit any current classification. An otherwise healthy 54-year-old man presented to the Dermatology department with a 5-month history of a nontender mass over his left posterior shoulder. He had originally presented to general surgery, who, along with specialist orthopaedic teams, had conducted multiple radiological and histopathological investigations. Imaging with ultrasonography and magnetic resonance imaging showed a complex subcutaneous mass and was nondiagnostic. Core biopsies were suggestive of an unusual myxoid lesion with a heavy chronic inflammatory component. As a diagnosis of sarcoma could not be excluded, the patient was referred to the Plastic Surgery department for wide local excision, and the plastic surgeon sought a preoperative opinion from Dermatology. On examination in the Dermatology clinic, a collection of deep, grape-sized, mobile, soft to firm nodules was palpable over the patient’s left scapula and deltoid region (Fig. 1). There was no lymphadenopathy, and no other body sites were affected. Blood tests, including inflammatory markers, autoimmune and infection screens, were normal or negative. Histological examination of a deep incisional biopsy revealed a normal epidermis and a mild upper and deep dermal perivascular inflammatory cell infiltrate composed of lymphocytes and plasma cells, with multifocal areas of mucin deposition separating collagen fibres in the mid to deep dermis and extending into the subcutis (Fig. 2a). Alcian Blue staining was strongly positive (Fig. 2b). The inflammatory cell infiltrate, including polytypic plasma cells, also surrounded and infiltrated small nerves (Fig. 2c). The histological diagnosis of a localized deep dermal and subcutaneous mucinosis of unknown aetiology was suggested. No intervention was undertaken, follow-up magnetic resonance imaging remained stable, and repeat clinical assessment revealed almost complete resolution at 6 months and complete resolution at 2 years. Lichen myxoedematosus (LM), or papular mucinosis, is a type of primary cutaneous mucinosis. The Correspondence: Dr Helen E. Lotery, Department of Dermatology, Royal South Hants Hospital, Brintons Terrace, Southampton SO14 0YG, UK E-mail: [email protected]