Alerts and Notices
SynopsisTrichomycosis axillaris is an asymptomatic superficial bacterial infection caused by Corynebacterium spp. It is relatively common and is the result of bacterial overgrowth, with concretions forming on hair shafts in moist regions of the body. These concretions represent bacterial colonies and the insoluble cement substance elaborated by the bacteria that adheres to the hair shaft.
Trichomycosis axillaris affects chiefly the hair of the axilla but may, to a lesser extent, involve the pubic hair as well (trichomycosis pubis). It may affect any age group from puberty through adulthood. The condition appears to affect men more often, likely because many women shave the axillary hair.
Recent evidence suggests that patients with one cutaneous disease process caused by Corynebacterium, such as trichomycosis axillaris, may often have other related and coincidental disease processes caused by the same bacterial species, such as pitted keratolysis (a corynebacterial infection of the feet) or erythrasma (a corynebacterial infection of the intertriginous skin).
A48.8 – Other specified bacterial diseases
49894005 – Trichomycosis axillaris
Differential Diagnosis & Pitfalls
- Black piedra and white piedra – A fungal infection consisting of darkly pigmented (black) or lightly pigmented (white) concretions on the hair that are firm (black) or soft and gelatinous (white). The scalp is preferentially involved in piedra, and hair breakage is more common than in trichomycosis axillaris. A potassium hydroxide (KOH) examination reveals hyphae.
- Hair casts – Parakeratotic scale that encircles the hair and may be freely moved up and down the shaft. These casts are often found in association with inflammatory conditions, such as seborrheic dermatitis or psoriasis.
- Pediculosis – Pediculosis pubis (the crab louse) may occasionally form nits on the pubic hair that are fixed. Upon microscopic examination, the adult louse is identified on the hairs near the base.