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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.
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.4 Three clinical types of congenital smooth muscle hamartoma are described: classic, papulo-follicular and mixed. The classic form presents as a well-limited skin-coloured or pigmented plaque covered with prominent overlying hypertrichosis. Over time, the congenital smooth muscle hamartoma grows in size, proportional to the child’s growth though hyperpigmentation and hypertrichosis contrarily tend to diminish.5
This case is unique as it is a nodular and nodulo-plaque presentation of congenital smooth muscle hamartoma associated with pain, which is not yet described in the existing literature.
Smooth muscle hamartoma can have a presentation as described in our case, that is, segmental nodular plaques associated with pain.
Dermoscopy of this tumour is not yet described in an adult (in existing literature), so our findings will assist in dermoscopic description of future cases.
Dermosocpy of smooth muscle hamartoma in our case includes pseudo-pigment network, milia-like cysts and light brown structureless areas.
Patient consent for publication
Contributors NKK and PS had full access to all of the data in the study and take responsibility for the integrity and accuracy of the data. Study concept and design—NKK. Acquisition, analysis and interpretation of data—PS and AD. Drafting of the manuscript—PS and AD. Critical revision of the manuscript for important intellectual content—NKK.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.