Unique case of perianal trichostasis spinulosa

Introduction

Trichostasis spinulosa (TS) is a follicular disorder characterized by the retention of vellus hairs, ranging from 5 to 40, in a follicle, most commonly found on the face, chest, and back.¹ On histopathology, TS consists of vellus hairs in a dilated infundibulum, typically together with keratinized material.¹ A single institution study in Yemen reported the prevalence to be 11.9%,² but TS has been reported to be an underdiagnosed disorder.^1,3 TS has been found to be present among all age groups.³ The etiology is currently unknown. Here, we describe a unique case of TS in a previously unreported perianal location.

Case report

A 64-year-old woman with a history of nonmelanoma skin cancers and substantial ultraviolet light exposure presented with acute subcutaneous swelling in the perianal region. Initially, it was erythematous, edematous, and painful (Fig 1). Patient noted that she rubbed a soap embedded with abrasive materials directly on her skin, including the perianal area, which raised the concern of foreign body particulates in the skin. Dermatoscope examination revealed tufted, fibrillar matter which was extracted using tweezers from perianal skin follicles. We compared the collected material to particulate matter extracted from 2 bars of exfoliating soaps that the patient had recently started using, 1 containing lavender blossoms and the other cedar leaf, cedarwood, fresh pine, and sage, per manufacturer’s information (Pre de Provence); the extracted patient specimen and soap materials were dissimilar (Fig 2). Upon closer examination under the dermatoscope, the matter removed from the patient’s perianal skin consisted of a uniformly shaped bundle of vellus hair that most closely resembled TS (Fig 3). Relief was rendered after hair tuft removal with tweezers, so no further treatment was recommended.

Fig 1.

Three lesions of trichostasis spinulosa of varying sizes at 7 o’clock perianal region 10 days prior to presenting to clinic (A). Same perianal area 9 days prior to presenting to clinic (B). Note comedonal appearance in (B).

Fig 2.

Patient specimen (A) compared with particulates from the lavender bar soap (B), and from the sage bar soap (C) observed using a light microscope. Scale bar = 1 mm.

Fig 3.

Postremoval dermascopic examination reveals tufted hair bundles (A and B) resembling “sheaves of wheat” characteristic of trichostasis spinulosa (B).

Discussion

TS has been reported to be associated with continuous pressure by garments⁴ and environmental irritants such as dust, oils, and ultraviolet light.¹ The location of TS in this patient may be related to constant pressure applied to the perianal area from sitting, which is akin to what has been speculated in belt wearing as the cause of TS on the lower abdomen.⁴ The patient’s TS appeared after usage of new sage and lavender soaps, containing oils, fats and abrasive material, which may have caused irritation to the area. Additionally, the patient’s history of ultraviolet light exposure (patient reported nude sunbathing and use of tanning beds), resulting in her history of nonmelanoma skin cancers, may have also played a role in TS development.¹ However, these associations may not fully explain the rare occurrence of TS reported in the perianal location. There may be underreporting and underdiagnosing of perianal TS due to its discrete location and normally asymptomatic nature.⁴

Since TS of the perianal region has not been reported previously, and previous clinical descriptions of TS mainly are of the nose and cheeks, the differential diagnosis included the consideration of pili multigemini (PM).

PM is commonly believed to be a rare developmental abnormality of the hair follicle, occurring in only 2% of the population.⁵ PM is composed of multiple hair shafts, enclosed in 1 outer root sheath, sprouting from 1 follicle.¹ While TS is thought to be caused by the retention of telogen hairs in a follicle during the growth of an anagen hair, PM results from a composite papilla with multiple hair shafts in the same growth stage.⁶ Both conditions are diagnosed clinically. TS is described in older adults, such as our patient, while PM is seen in children and adolescents; TS lesions are described as resembling a “comedone-like, spinus plug” with vellus hairs, as in our patient (Fig 1, B) compared to the mature, thicker hairs seen in PM; and TS is associated with the occurrence of skin cancers, as in our patient, while PM is not.¹ The perianal location of our patient’s lesion was unusual: there have been no prior reports of perianal TS. Although TS can be diagnosed clinically, a limitation of this study is the lack of a skin biopsy and a histopathological analysis of the lesion.

Differentiating TS from PM is clinically useful, since suggested treatments for TS and PM differ. Emollients, retinoids, and lasers have been proposed to be effective treatment options for TS,¹ whereas Q-switched ruby laser has been shown to be efficacious for a large area of PM on the beard in 1 case report.⁵

This is the first report of TS in the perianal area, which was the source of painful folliculitis after irritation with abrasive material in soaps. This case illustrates the benefit of using the dermatoscope and microscopic exam of matter removed from the skin to facilitate a clinical diagnosis.

Conflicts of interest

None disclosed.