Multiple acquired smooth muscle hamartomas with thick‐walled blood vessels on scalp

Abstract

Smooth muscle hamartoma (SMH) is a benign hamartomatous condition that consists of a dermal proliferation of smooth muscle cells. We hereby report a case of multiple, acquired SMHs on scalp. A 25-year-old male had a 6-year history of multiple, asymptomatic, hyperpigmented plaques on the scalp which were progressively increasing in number and size. Histopathological examination revealed large thick-walled blood vessels, in addition to the haphazardly arranged discrete smooth muscle bundles in the reticular dermis. This case of SMH is unusual in being acquired, having multiple lesions, involving scalp, and having thick-walled blood vessels apart from arrector pili muscle bundles. It emphasizes the wide spectrum of clinical and histopathological variations that may be associated with acquired SMH.

Smooth muscle hamartoma and striated muscle hamartoma: Clinicopathologic characterization of two rare entities and literature review

“…Although the etiopathogenesis of the SMH remains unclear, cases can be divided into two groups: congenital 1,5,9,10,16‐24 and acquired SMH 2‐4,6‐8,11,12,15,25‐32 . Eleven of our cases (41%) presented as a congenital lesion, most commonly located on the torso and lower extremity (six cases, 55%) followed by the upper extremity (two cases, 18%) and the head and neck area (two cases, 18%), and one case (9%) was located on the penile shaft.…”

Acquired smooth muscle hamartoma: A case report on the lower extremity with hidrosis

“…In a review of the published biopsy-proven cases of ASMH, Jain et al 2 found that the age of presentation ranged between 12 and 64 years. In addition, reported sites for ASMH include the scalp, upper extremity (upper arm, forearm and shoulder), chest and genitalia (scrotum, penis and labia majora).…”

“…ASMH clinically presents as a solitary, often indurated plaque which may have superimposed small papules. Jain et al 2 reported a case of ASMH which presented as multiple lesions on the scalp. As demonstrated by our patient, associated hyperpigmentation and hypertrichosis are not common with ASMH compared with congenital SMH.…”

“…1 Pseudo-Darier sign is usually negative in ASMH. 2 While most lesions are asymptomatic, pain and pruritus have been reported with ASMH. 3,5 To our knowledge, this is the first case of ASMH to be present along with hidrosis.…”

“…As demonstrated by our patient, associated hyperpigmentation and hypertrichosis are not common with ASMH compared with congenital SMH. 2 Transient elevation or pilo-erection induced by rubbing is referred to as pseudo-Darier sign; it is a characteristic finding for congenital SMH. 1 Pseudo-Darier sign is usually negative in ASMH.…”