Congenital smooth muscle hamartoma: an atypical presentation

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 nodulo-plaques were noted, arranged in segmental distribution over the left side of mid-back (figure 1). On palpation, lesions were tender to touch and firm in consistency, though rubbing of lesions did not reveal any changes (pseudo-Darier sign). There was no overlying hypertrichosis. Dermoscopic examination revealed a pseudo-pigment network, milia-like cysts and light brown structureless areas (figure 2). Based on salient history and examination points, segmental dermatofibroma,1 leiomyoma,2 and smooth muscle hamartoma and schwannoma3 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 cigar-shaped 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. © BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.