Dermoscopy of Yellow Concretions on Axillary Hair

Question

A healthy man in his early 20s presented to the dermatology clinic with a several-month history of sticky and malodorous axillary hair. Despite the use of antiperspirant, he complained of foul-smelling armpits and profuse sweating that has worsened in the last few weeks. Physical examination revealed thick, yellowish material along several hair shafts of the axilla (Fig. 1a) and presence of rancid axillary odor. Dermoscopic evaluation revealed thick, irregular, waxy, yellowish-white concretions along the hair shafts (Fig. 2a).

Fig. 1.

Gross findings. Clinical photograph of axillary hair from case 1 showed thick, dense yellowish material adhered to the axillary hair shafts (a). Physical examination of case 2 revealed slightly thinner adherent concretions with an ashier hue when compared to case 1 (b).

Fig. 2.

Dermoscopic findings. Polarized dermoscopy of case 1 revealed thick, waxy, yellowish-white adherent masses dispersed throughout the hair shafts (a). In case 2, axillary hairs were seen surrounded by irregular nodules and concretions of different thicknesses and contours (b).

Similar to the first case, during a routine full-body skin examination, a man in his mid-20s was discovered to have sticky whitish-yellow material around the underarm hair (Fig. 1b). The patient was not aware of the problem and denied any other symptoms, including strong axillary odor or hyperhidrosis. Dermoscopy of involved hairs demonstrated chalky, yellowish-white nodules dispersed throughout the hair shafts (Fig. 2b). Given the clinical presentation and dermoscopic assessment ...

What is your diagnosis?

Answer

Trichomycosis axillaris (TA), also called trichomycosis palmellina or trichobacteriosis, is a common bacterial infection caused by the genus Corynebacterium spp. Corynebacterium tenuis [1] and Corynebacterium flavescens are common gram-positive diphtheroids that colonize the hair of the axilla, and less commonly the pubic, perianal, and scalp regions. Young adults, especially men, are more commonly affected [2]. Predisposing factors include poor local hygiene, hyperhidrosis, obesity, and warm, humid climates [1].

Trichomycosis flava, rubra, and nigra are the three clinical forms of trichomycosis, out of which flava is the most common. Odorous mucoid sheaths are formed when bacteria colonize the hair shafts surrounded by dried apocrine sweat, and subsequently produce a cementing material that encases the hair. Together, these substances generate creamy, sticky concretions that are malodorous and visibly disturbing for patients. Thick, irregular yellowish-brown or white nodules are seen throughout the affected hairs, typically sparing the hair root and adjacent skin [2]. Red or black nodules can also be found [3].

Clinical findings are sufficient for diagnosis; however, dermoscopy, Wood light, and direct microscopic examination with KOH and/or Gram stain are additional techniques that can be used to support the diagnosis. Although generally asymptomatic, most patients seek care due to unpleasant odor. Bacterial metabolism of testosterone results in production of compounds that yield an acidic, rancid odor. Dermoscopy reveals waxy yellowish-white or brown nodules and concretions adherent to the hair. Reports of characteristic dermoscopic signs have also been published, such as the feather sign, brush sign, plume sign, and skewer sign, yet we believe these metaphors are often difficult to identify and unnecessary to describe observed findings [4, 2]. Other dermoscopic findings include adherent concretions with a rosary of crystalline stone appearance [2]. Dermoscopy is a useful tool to better visualize bacterial concretions and confirm the clinical diagnosis. Wood lamp examination of affected hairs produces a weak, yellowish fluorescence. Potassium hydroxide test exposes yellowish material of minimal translucency surrounding, yet commonly not invading, the hair cortex [5]. Light microscopy of Gram-stained preparations of hair concretions reveals purple rods and coccobacilli [6].

The clinical differential diagnosis includes trichomycosis nodularis, pseudonits, and pediculosis. Trichomycosis nodularis, a superficial fungal infection also known as piedra, affects the hair shafts of the axillary, scalp, and genital region. In white piedra, the hair shaft is covered by soft yellow-white fusiform nodules, which are easily detachable. Black piedra, a subtype more common in tropical climates, presents with firmly attached black-brownish nodules. However, piedra can be differentiated from TA by KOH testing, which reveals fungal hyphae surrounding the hair shafts. Pseudonits or hair casts result from epidermal parakeratosis triggered by inflammation or abnormal keratinization of the follicular infundibulum, they surround the hair shaft and are seen on the scalp and eyelashes. Microscopic examination or culture of affected hairs are negative for organisms, unlike in TA [5]. Pediculosis is a lice infestation caused by a variety of different organisms such as Pediculus humanus var. capitis. Diagnosis is made by clinical examination, which reveals nits attached to the hair. Pruritus is a common complaint.

Complete resolution can be achieved by general hygiene measures, such as shaving off all the axillary hairs and maintaining the area dry. Topical treatments, such as topical benzoyl peroxide, erythromycin, or clindamycin, can be applied to expedite bacterial clearance and prevent recurrence [5]. Antiperspirants containing 15–20% aluminum chloride hexahydrate solution and drying powders are recommended to decrease sweating and reduce the risk of bacterial regrowth [5, 6]. The first case, the man in his early 20s, achieved rapid resolution after shaving the axillary hairs and applying prescription antiperspirants. The second case, however, refused to shave the axillary hair and denied treatment with topical erythromycin gel. He attempted to treat himself with essential oils, but did not achieve any therapeutic success.

We have herein reported 2 cases of TA corroborated by dermoscopic findings. Dermoscopy is a simple noninvasive technique that can confirm a clinical suspicion of TA. The prevalence of this condition is likely underestimated because of its relatively asymptomatic clinical course.

Statement of Ethics

The authors have no ethical conflicts to disclose.

Disclosure Statement

There were no funding sources for this work. Ms. Cervantes and Dr. Johr have no conflict of interest to declare. Dr. Tosti's conflict of interests: P&G: consultant. DS Laboratories: consultant. Incyte: PI. Pfizer: PI. Valeant: consultant. PharmaDerm: speaker bureau. Springer, Taylor & Francis: author royalties. Karger: editor-in-chief.