Tinea capitis in the form of concentric rings in an HIV positive adult on antiretroviral treatment.

Dermatophyte infection may present in the form of concentric rings caused by Trichophyton concentricum, known as Tinea Imbricata. In immunosuppressed patients, there are reports of lesions in the form of concentric rings caused by dermatophytes other than Trichophyton concentricum too, mostly by Trichophyton tonsurans, known as Tinea indesiciva or Tinea pseudoimbricata. We report a case of tinea capitis in a HIV-positive adult woman on antiretroviral therapy, who presented with concentric rings of papules and pustules with slight scaling on the scalp along with diffuse thinning of hair. Both Potassium hydroxide mount and culture showed the presence of Dermatophytes. Tinea capitis is considered rare in adults, but new cases are being reported in immunocompromised as well as in immunocompetent patients. The pertinent features of this case are: HIV-positive adult female on antiretroviral therapy, presenting with tinea capitis in the form of concentric rings; culture from the lesion grew Microsporum audouinii; responding to oral Terbinafine.

Introduction

Tinea imbricata or Tokelau is fungal infection of the skin, which manifest with multiple concentric rings of erythematous papules, pustules, scaling and crusting, caused by Trichophyton concentricum, an anthrophphillic dermatophyte. Tinea pseudoimbricata or tinea indecisiva are the terms given for similar clinical presentations caused by fungal agents other that Trichophyton concentricum, like Trichophyton tonsurans, mainly in patiets with prolonged use of steroid and anti fungal topical medications or inadequate treatment with anti fungal agents leading to re-infection by the same pathogen, forming concentric rings. Genetic, environmental and immunological factors play a major role in development of this disease. Decreased immune response to Trichophyton concentericum is well known in patients of Tinea imbricata. Diagnosis can be easily made by clinical examination because of its characteristic appearance. Scrapings from the affected skin show fungal hyphae and culture on Sabouraud's dextrose agar or Mycosel agar (Sabouraud's medium plus cycloheximide and chloramphenicol to inhibit bacterial growth) grow fungal colonies in 8-15 days. Many treatments have been used for managing Tinea Imbricata. General guidelines include use of combined systemic and topical anti fungal agents.

Case Report

A 35-year-old HIV-positive woman presented to us with concentric rings of pustules and papules, with multiple rings of scaling present on almost the entire scalp, extending on to the forehead anteriorly, along with diffuse thinning of hair [Figures 1 and 2]. Her CD4 lymphocyte count was 99cells / (mm)3 and she was receiving treatment with zidovudine, efavirenz, and cotrimoxazole, for the last 15 days. There was no family history of any skin complaint. Scraping from the lesion showed fungal hyphae on Potassium hydroxide (KOH) examination, and culture from the sample taken from the scalp grew Microsporum audouinii. The patient was treated with terbinafine 250 mg daily for three weeks and she had complete clinical and microbiological clearance at three weeks.

Figure 1

Concentric rings of papules and pustules with scaling

Figure 2

Concentric rings of tinea capitis extending to the face

Discussion

Tinea capitis is considered rare in adults and usually accounts for less than 3% of all tinea capitis cases,[1-3] although reports of incidence as high as 11% are reported in the literature.[4] Tinea capitis is considered rare after puberty because of certain protective factors,[35-8] namely the fungistatic property of the increased sebum, sweat, greater thickness of hair, and presence of Pityrosporum ovale as a competing agent in this age group. The clinical presentation of tinea capitis varies in adults. In HIV patients, the rarity of tinea capitis has been explained by some[9] as being due to the increase in colonization of their scalp by Malassezia spp, thus competitively inhibiting the dermatophytes. Predisposing factors for tinea capitis in adults have been thought to be; impairment of health, source of fungal infection somewhere else on the body, children, zoophilic sources like pets, hormonal changes as in postmenopausal women, and so on.

However, unusual presentations are not uncommon in HIV-positive patients. A high degree of clinical suspicion and a careful mycological study are essential to diagnose it. The current patient presented with concentric rings of pustules and papules limited to the scalp. The KOH examination showed fungal hyphae. A culture on Sabouraud's dextrose agar with antibiotics grew Microsporum audouinii. An asymptomatic adult carrier state is also not a rare event.[6]

Tinea Imbricata manifests in the form of concentric rings on the body caused by Trichophyton concentricum. The occurrence of concentric rings has been explained in literature as being due to a negative, delayed-type hypersensitivity to the Trichophyton concentricum cytoplasmic antigen and T-lymphocyte hyporeactivity,[10] thus leading to a ring- within-a-ring formation. There are reports of patients presenting with tinea in the form of concentric rings caused by dermatophytes other than Trichophyton concentricum, mostly by Trichophyton tonsurans and Microsporum gypseum.[11-13] In all such cases reported as Tinea pseudoimbricata or Tinea indecisiva, patients were either systemically or locally immunosuppressed. Perhaps these cases simulated the mechanism of T-cell hyporeactivity and lack of delayed-type hypersensitivity to Trichophyton concentricum as seen in Tinea Imbricata. The current patient, who was HIV positive and had a CD4 count of 99 cells / (mm)3, presented with a similar clinical presentation on the scalp, however, the culture grew Microsporum audouinii.

Cell-mediated immunity is the primary defense against fungal infections, although patients with tinea capitis usually develop specific antifungal antibodies, but these have a minor role. The clinical resemblance of such cases may be due to similar immunosuppressive processes involving the T cells. As in Tinea Imbricata, T-cell hyporeactivity allows sequential waves of infection and immune response, leading to a ring-within-a-ring formation. The same process might explain the current case also, as T-cells are the major target in HIV infection.

The treatment of tinea capitis in HIV-positive adults is not more difficult than in immunocompetent patients.[5] However, it is well known that in HIV-infected patients, adverse drug reactions are more common and a lower gastric acidity in such immunosuppressed patients causes diminution of drug absorption. Our patient has been clinically and microbiologically (post three weeks of treatment, KOH and culture were negative) treated with Terbinafine 250 mg daily for three weeks, but some have reported difficulty in treating cases of tinea capitis in HIV patients.[14] Prolonged treatment may be necessary and also due to the presence of achlorhydria, the dose of the anti-fungal may have to be increased. Relapses are also known to be more frequent in HIV-infected patients. Thus, not only can tinea capitis in immunosuppressed patients have atypical presentations, but it can also be refractory to treatment, with frequent relapses.