Myokymia as a Presenting Sign of Congenital Smooth Muscle Hamartoma

Abstract

We report a 4-week-old male infant with intermittent asymptomatic bouts of vermicular movements of the skin (myokymia). Myokymia started at the age of 4 days. Attacks occurred approximately every 30-60 minutes and could be elicited by gently stroking the skin. Macroscopically no abnormalities typical for smooth muscle hamartoma such as hypertrichosis or hyperpigmentation were observed. Histologic examination of a skin biopsy specimen showed bundles of hyperplastic smooth muscle tissue within the reticular dermis which were associated with hair follicles. Karyotyping did not reveal any structural or numeric chromosomal anomaly. The findings led to the diagnosis of congenital smooth muscle hamartoma. On follow-up at the age of 24 months myokymia persisted, but with a marked reduction in the number of attacks per day. The phenomenon of myokymia results from neurally induced spontaneous contraction of dermal smooth muscles. It is also known as "pseudo-Darier's sign." While most of those affected previously reported had hypertrichosis or hyperpigmentation, this patient seems to be the first to present with myokymia alone.

Cutis marmorata telangiectatica congenita‐like lesion with fibrotic appearance

“…The first consists of transient elevation of the lesion with piloerection and sometimes whitening after rubbing, and myokymia refers to spontaneous transient episodes of vermiform movement of the involved area. 4,5 Our case represents an unusual form of SMH. The lesion closely mimicked cutis marmorata telangiectatica congenita (CMTC) and even contained atrophic areas.…”

“…Further clues for SMH are the pseudo‐Darier sign and myokymia. The first consists of transient elevation of the lesion with piloerection and sometimes whitening after rubbing, and myokymia refers to spontaneous transient episodes of vermiform movement of the involved area …”

More than goosebumps: A case of marked skin dimpling in an infant

“…Prior to this seminal report, very few cases of a similar phenomenon had been described in the literature . Early reports postulated hyperplastic smooth muscle as the underlying etiology for the observed clinical syndrome, occasionally leading to provisional diagnoses of congenital smooth muscle hamartoma (CSMH) . In such cases, histologic examination purportedly revealed hyperplastic smooth muscle tissue, though further review of the pathologic images called into question the true degree of hyperplasia .…”

“…The term infantile transient smooth muscle contraction of the skin (ITSMC) was initially coined in 2013 by Torrelo et al when describing a series of nine infants who experienced “transient rippling of the skin” in response to various stimuli . Prior to this seminal report, very few cases of a similar phenomenon had been described in the literature . Early reports postulated hyperplastic smooth muscle as the underlying etiology for the observed clinical syndrome, occasionally leading to provisional diagnoses of congenital smooth muscle hamartoma (CSMH) .…”

“…By comparison, bilateral lower extremity involvement is common in ITSMC, though truncal involvement has also been reported . Finally, if a skin biopsy is performed, CSMH will classically demonstrate discrete bundles of haphazardly arranged smooth muscle fibers in the dermis, whereas biopsy of ITSMC may or may not reveal hair follicle–associated smooth muscle hyperplasia …”