Acquired smooth muscle hamartoma with sebaceous component / Hamartoma de músculo liso adquirido con componente sebáceo

Abstract Background: Acquired smooth muscle hamartoma (ASMH) is a rare benign lesion characterized clinically by hyperpigmented plaques with hypertrichosis and some follicular papules. The main histologic finding is the presence of disorganized smooth muscle bundles in the dermis. Only 25 cases of ASMH have been reported in the literature. Clinical case: We present the case of an 18-year-old male who reported a pigmented area and increased hair growth on the left hemifacial with one year of evolution. Clinically, a plaque was observed in the preauricular region and on the left cheek with a linear Blaschkoid path, consisting of hyperpigmentation, hypertrichosis, and some papular lesions, with negative pseudo-Darier sign. Histological analysis showed an increase in the number of smooth muscle bundles in the middle and deep dermis surrounding abundant sebaceous glands and numerous hair follicles in different stages of evolution. Conclusions: The sebaceous component in this lesion was prominent. Therefore, we considered this lesion part of a spectrum where the acquired smooth muscle hamartoma and folliculosebaceous cystic hamartoma are found at the extremes. This case would fall in the middle of the range, as it combines both histological features.

Resumen Introducción: El hamartoma de músculo liso adquirido (HMLA) es una lesión benigna adquirida, poco frecuente, caracterizada clínicamente por presentar placas hiperpigmentadas, con hipertricosis y algunas pápulas foliculares. El principal hallazgo histológico es la presencia de abundantes haces de músculo liso desorganizados en la dermis. Se han reportado solo 25 casos de HMLA en la literatura. Caso clínico: Se presenta el caso de un paciente de sexo masculino de 18 años que refirió una zona pigmentada y el aumento de vello en la hemicara izquierda con un año de evolución. Clínicamente se observó una placa en la región preauricular y mejilla izquierda con trayecto lineal blaschkoide, constituida por hiperpigmentación, hipertricosis y algunas lesiones papulares, con signo pseudo-Darier negativo. Histológicamente se encontró un aumento en el número de haces de músculo liso en la dermis media y profunda rodeando abundantes glándulas sebáceas, así como numerosos folículos pilosos en diferentes estadios de evolución. Conclusiones: El componente sebáceo en esta lesión fue muy marcado, por lo que se considera que forma parte de un espectro donde en los extremos se encuentran el hamartoma de músculo liso adquirido y el hamartoma quístico folículo sebáceo. El presente caso se encontraría en medio, ya que combina ambas características histológicas.

A Case of Acquired Smooth Muscle Hamartoma on the Sole

A smooth muscle hamartoma is a benign proliferation of smooth muscle bundles within the dermis. It arises from smooth muscle cells that are located in arrector pili muscles, dartos muscles, vascular smooth muscles, muscularis mammillae and the areolae. Acquired smooth muscle hamartoma (ASMH) is rare, with only 10 such cases having been reported in the English medical literature to date. Most of these cases of ASMH were shown to have originated from arrector pili and dartos muscles. Only one case was reported to have originated from vascular smooth muscle cells. A 21 year-old woman presented with a tender pigmented nodule, with numbness, on the sole of her foot, and this lesion had developed over the previous 18 months. The lesion showed no hyperpigmentation or hypertrichosis, and the biopsies demonstrated increased smooth muscle bundles in the dermis, and especially around the blood vessels. Moreover, the specimens stained positive with Masson trichrome stain and alpha-smooth-muscle actin antibodies, thus supporting our diagnosis of ASMH of the foot sole. Herein, we report on a rare case of ASMH on the foot sole, and this lesion originated from vascular smooth muscle cells. This type of case has not been previously described in the English medical literature.

A Case of Acquired Smooth Muscle Hamartoma on the Sole / 대한피부과학회지

Smooth muscle hamartoma (SMH) is a benign proliferation of smooth muscle bundles within the dermis. It arises from either the arrector pili muscles, dartos muscles, smooth muscle cells in blood vessels and lymphatics, muscularis mamillae and areola, or cutaneous adnexa. Acquired smooth muscle hamartoma is very rare, and only 12 cases have been published to date. All reported cases are originated from arrector pili or dartos muscles. Herein, we describe a case of acquired smooth muscle hamartoma which originated from the smooth muscle cells in blood vessels of the right sole. To our knowledge, this is the first reported case which has originated from the smooth muscle cells in blood vessels.