. MG is a dermatophytic folliculitis that classically presents as folliculocentric plaque, in which there are papules, pustules, and nodules, usually found on the lower leg and almost exclusively in adults.1 Wrists are commonly affected as well.
MG is typically caused by mechanical disruption of hair follicles that allows fungi to penetrate deep into dermal tissue.2 Quite often, the source of infection is typically the patient’s skin or nails. Associated risk factors include longstanding fungal infection, shaving or other cutaneous trauma, topical steroids, and immunosuppressive therapy.3,4 Although MG can be caused by other fungal species, it is most often caused by Trichophyton rubrum or Trichophyton tonsurans.1 There are two types of MG, the perifollicular papular form, which is localized and typically occurs in healthy individuals, and the deep subcutaneous plaque or nodular forms that usually occur in immunocompromised individuals.5
MG is an important clinical manifestation to be familiar with because of the increase in the numbers of solid-organ transplants and patients on immunosuppressive therapies. These patients are highly predisposed to opportunistic infections with aggressive clinical courses and will usually require prolonged treatment as relapses are common.3,5
Tissue culture and skin biopsy are often needed to establish the diagnosis. If a topical antifungal has been used, KOH (potassium hydroxide) and culture may be negative. This patient’s tissue culture was positive for T. rubrum. The histopathology revealed hyperkeratosis and acanthosis with focal parakeratosis and a lymphohistiocytic infiltrate in the dermis. On PAS (Periodic acid–Schiff ) stain, PAS-positive hyphae were identified in the keratin layer, confirming a diagnosis of tinea infection.
First line treatment includes systemic antifungals such as griseofulvin, ketoconazole, itraconazole, and terbinafine. Duration of therapy is typically 4-8 weeks or until all lesions are cleared.3,5
This case and photo were submitted by Mr. Hakimi of University of California San Diego School of Medicine and Dr. Sateesh of San Diego Family Dermatology. Donna Bilu Martin, MD, edited the column.
Dr. Bilu Martin is a board-certified dermatologist in private practice at Premier Dermatology, MD, in Aventura, Fla. More diagnostic cases are available at . To submit a case for possible publication, send an email to .
1.“Fitzpatrick’s Dermatology in General Medicine” (New York: McGraw-Hill Medical, 2012).
2. Bonifaz A et al..
3. Romero FA et al.
4. Chou WY, Hsu CJ. Medicine (Baltimore). 2016 Jan;95(2):e2245..
5. Ilkit M et al..