LAUSR

© BMJ Publishing Group Limited 2022. No commercial reuse. See rights and permissions. Published by BMJ. DESCRIPTION A man in his early 40s presented to our hospital with painful skin lesions over his back. The lesions were present since birth but had progressively increased in size and were painful every winter. On examination, multiple clustered skin coloured to hyperpigmented nodules and noduloplaques were noted, arranged in segmental distribution over the left side of midback (figure 1). On palpation, lesions were tender to touch and firm in consistency, though rubbing of lesions did not reveal any changes (pseudoDarier sign). There was no overlying hypertrichosis. Dermoscopic examination revealed a pseudopigment network, milialike cysts and light brown structureless areas (figure 2). Based on salient history and examination points, segmental dermatofibroma, leiomyoma, and smooth muscle hamartoma and schwannoma were considered as possible differentials, and a punch biopsy for histopathological examination was performed. Histopathological examination revealed a proliferation of haphazard interlacing fascicles of mature smooth muscle cells with a central cigarshaped nucleus and fibrillar and eosinophilic cytoplasm (figures 3 and 4). Epidermal features included basal layer pigmentation, mild acanthosis and hyperkeratosis. There was no evidence of necrosis, mitosis or atypia. After clinical and histopathological correlation, a final diagnosis of smooth muscle hamartoma was considered and tablet nifedipine was prescribed to the patient for pain relief (symptomatic management) as the patient denied surgical or laser intervention. Congenital smooth muscle hamartoma is a benign proliferation of mature smooth muscles, usually presenting as a solitary lesion. There is no risk of malignant transformation of this tumour; therefore, no treatment is necessary in most cases. Three clinical types of congenital smooth muscle hamartoma are described: classic, papulofollicular and mixed. The classic form presents as a welllimited skincoloured or pigmented plaque covered with prominent overlying hypertrichosis. Over time, the congenital smooth muscle hamartoma grows in size,