Trichostasis Spinulosa at an Unusual Site.

Trichostasis spinulosa (TS) is very common yet unrecognized disorder of the hair follicle. Usually occurring on the mid-face, especially on the nose, TS occurs more commonly in young, adult dark skinned women. Here, we present a case of TS at an unusual site diagnosed on the basis of history, hair mount, dermoscopy, and histopathology.

INTRODUCTION

Trichostasis spinulosa (TS) is very common yet unrecognized disorder of the hair follicle. It results from the retention of numerous vellus hairs (range, 5–62; average, 12) surrounded by a keratinous sheath in a dilated follicle.[1] It can occur anywhere in body, but the usual site is nose. It can also be found on the forehead, face, chest, intrascapular area, and the arms.[2] The case is presented for its rarity as the axilla has not been found to be a common site of TS.

CASE REPORT

A 40-year-old female presented with gradually erupting asymptomatic black-colored raised lesions in the bilateral axillae for the past 15 years. She could remove the lesions using gentle pulling with nails without any discomfort. She also complained of sparse hair in the axillae since puberty. Her medical or family history was unremarkable and did not take any regular medication. Examination revealed multiple dark-black keratotic follicular papules of the size of pinheads (0.5–1 mm) with sparse hair in the bilateral axillae [Figure 1a and b]. Hair mount of an extracted plug revealed multiple-coiled vellus hairs embedded in keratinous material [Figure 2]. Further, dermoscopy of lesions revealed black dot-like structures, which were indeed tufts of light pigmented vellus hairs, tightly held together inside one follicular opening [Figure 3]. Histopathology of a lesion revealed two cystically dilated hair follicles with retention of small hair shafts and keratinous material within the dermis along with perifollicular mononuclear cell infiltrate [Figure 4]. Based on the above feature, a diagnosis of TS was made. The patient was advised 0.04% tretinoin cream at night for local application on the affected area without much relief.

Figure 1

(a and b) Multiple dark black keratotic follicular papules with sparse hair in the bilateral axilla

Figure 2

Multiple coiled vellus hairs embedded in keratinous material

Figure 3

Black dot-like structures

Figure 4

Dilated hair follicle with retention of small hair shafts and keratinous material within the dermis along with perifollicular mononuclear cell infiltrate

DISCUSSION

TS is relatively common disorder of pilosebaceous unit. It appears as slightly raised, small (1 mm), dark follicular spines that must be distinguished from open comedones (blackheads). The disorder was first recognized by the German dermatologist Felix Franke in 1901, who named it “Pinselhaar” (paintbrush hair). The term “trichostasis spinulosa” was introduced in 1913 by Noble.[3] It is common in both the sexes. There exist two variants: (1) The classical variant presenting with a nonitching, comedo-like lesion on the face in the elderly; (2) the pruritic variant presenting with itching, follicular papules located on the limbs in young adults.[4]

Exact etiology of TS is not known. Suggested causes of TS include acquired hyperkeratosis of the follicular infundibulum by internal factors with comedo formation, augmented clinical activity of hair papillae, congenital multiple papillae in one follicle (pili multigemini), continuous local pressure by garments, dislocation of the follicular axis, endocrine and metabolic disorders, and by external factors, for example, exposure to fat, dirt, heat, irritants, and vitamin deficiency.[35] A study suggested that microorganisms such as pityrosporum and bacteria, especially Propionibacterium acnes may be one of the possible etiologic factors of TS.[6] Further, minoxidil-induced TS of terminal hair[7] and possible association with prolonged topical application of clobetasol propionate have been suggested in a case report.[8]

Treatment for TS includes hydroactive adhesive pads (Biore), topical keratolytic agents, and retinoic acids but tends to recur after discontinuation of treatment. Lasers such as 800 nm pulse-diode and 755 nm alexandrite lasers have been reported to be effective in the removal of abnormal hair follicles.[9]

CONCLUSION

The presented case focuses our attention on presentation at unusual site, i.e. axillae in a common skin disorder which is underdiagnosed and unrecognized. In addition, investigations such as dermoscopy and KOH mounting of plucked hair helped in our diagnosis of TS.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.