Case Report
A 40-year-old French male patient was referred to us with a 7-year history of multiple pigmented macules on the trunk and extremities. The patient had no history of diabetes mellitus or injections, including steroids and insulin. No relevant clinical manifestations were observed among his family members. Physical examination revealed multiple, slightly depressed, and pigmented macules ranging from 1 to 3 cm in diameter without hypertrichosis on the trunk and extremities (Figure 1 ).
Histopathological examination demonstrated irregularly distributed, bundled pale eosinophilic structures of various sizes with oval-shaped nuclei in the upper dermis by hematoxylin and eosin staining (Figure 2a ). There was no discernible increase in the number of melanocytes in the epidermis or hair follicles. Masson trichrome staining showed that the irregularly distributed and variously sized bundled structures were less stained than collagen fibers in the dermis (Figure 2b ). These findings collectively indicated an aberrant proliferation of mature smooth muscle in the upper dermis. Based on these findings, the diagnosis of SMH was made. The patient was followed for 6 months, during which time there was no change in the cutaneous manifestations.