Itchy, red rash plagues teenager

THE CASE

A frustrated teenaged girl comes to your office complaining of an itchy, red rash on her right calf that she's had for 3 months. She has avoided sports because she is afraid to let the girls at school see her leg, which improves every time she applies a topical corticosteroid cream, but the rash recurs as soon as she stops.

DIAGNOSIS: Majocchi granuloma (dermatophyte granulomatous tinea corporis)

Other predisposing factors include chronic skin occlusion and systemic immunosupression.¹ Lesions may appear in any hair-bearing area including scalp, face, forearms, hands, or legs. Skin lesions usually manifest as grouped or isolated papules or nodules near the border of a plaque. Lesions may become suppurative if superinfection occurs.

Two types of Majocchi granuloma exist: follicular and subcutaneous nodular.¹ The follicular type usually presents as papules, pustules, and nodules in a follicular distribution within erythematous, scaling plaques. Distended hair follicles may also be observed.²

The subcutaneous nodular type typically occurs in chronically immunosupressed patients.¹ Lesions commonly manifest as subcutaneous nodules and plaques, with or without pustules.²

DIFFERENTIAL DIAGNOSIS

Majocchi granuloma may closely resemble bacterial folliculitis, acne keloidalis nuchae, herpes simplex infection including herpetic folliculitis, furunculosis, pseudofolliculitis barbae, Kaposi sarcoma, kerion, lymphocytoma cutis, and nodular scabies.²

The typical appearance of lesions combined with a history of topical steroid use, skin occlusion, or frequent shaving should raise the clinical suspicion for Majocchi granuloma. If a topical antifungal has been used recently, KOH examination and culture may be negative. In such cases, a biopsy may be needed for definitive diagnosis.³

ETIOLOGY

The most common organism cultured from Majocchi granuloma is Trichophyton rubrum or, less common, T mentagrophytes or Epidermophyton floccosum.² However, other dermatophytes have been reported to cause Majocchi granuloma.⁴

It is believed that the condition starts after physical trauma, and occlusion of hair follicles alters the structure. This serves as a portal of entry for the organism, together with keratin and other necrotic material, into the dermis.⁵ The dermatophyte invades the hair follicle and dermis, resulting in deep follicular papules and pustules and a foreign body granulomatous reaction.