Seborrheic dermatitis-like adult tinea capitis due to Trichophyton rubrum in an elderly man

Abstract

Adult tinea capitis is often neglected and misdiagnosed, especially in men. We herein reported an older man with seborrheic dermatitis-like tinea capitis caused by Trichophyton rubrum to raise awareness of the disease. Scale and alopecia were the critical diagnostic clues in this patient. Given the previous presence of tinea pedis and onychomycosis, relevant mycological examinations were promptly performed, and antifungal therapy, as well as patient education, were effectively administered.

1. Introduction

Tinea capitis, a public health concern, predominately occurs in prepubescent children and occasionally in adults, where it most commonly affects postmenopausal women, probably due to decreased estrogen levels and triglycerides in the sebaceous glands after menopause [1]. Trichophyton rubrum (T.rubrum) is the most common causative agent of skin and nails fungal infections but rarely causes scalp and hair infections [2]. In recent years, however, many investigations have reported that the prevalence of adult tinea capitis (ATC) is increasing, and a considerable proportion of it is infected by T.rubrum [3,4]. The clinical presentations of ATC are atypical and variable, depending on the types of pathogenic microorganisms, hair invasion, and host inflammatory response, which often lead to misdiagnosis and improper management. We herein reported an older man with seborrheic dermatitis-like tinea capitis caused by T.rubrum to raise awareness of the scalp disease in adult males.

2. Case presentation

A 77-year-old man visited the dermatology hospital with over six months history of furfur and itchy scalp (day 0). The patient developed scattered scaly scalp with obvious pruritus before six months. He had been diagnosed with “seborrheic dermatitis " in the other hospital and treated with selenium sulfide lotion and systemic Chinese medicine. However, the lesions gradually expanded with growing hair loss. On physical examination, diffuse and gray-yellow scaly erythema accompanied by scattered blood crusts, as well as sporadic hair loss, were observed on his parietal scalp (Fig. 1). In addition, he has been suffering from tinea pedis and onychomycosis for years without treatment, presenting as desquamation of toes, discoloration and thickening of most nail plates (S.1).

Fig. 1.

Clinical manifestations. Gray-yellow, adherent, and scaly erythema with blood crusts and localized hair loss were shown on the right parietal scalp. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Scale and alopecia were the critical diagnostic clues in this patient, and considering his history of superficial fungal infections, relevant mycological examinations were carried out quickly. Direct microscopic study of the lesion showed long and septate hyphae (day 0) (Fig. 2A). Fungal culture on potato dextrose agar established white and velvety colonies with red pigmentation (day +10) (Fig. 2B). After solid culture, the fungal protein was extracted by ethanol-formic acid extraction method, then 1ul of the protein was placed on the polished steel target plate, and 1ul of matrix solution was added, and finally put into the matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) EXS3600 (Zybio Inc., Chongqing, China) for analysis. As a result, T.rubrum was identified by the MALDI-TOF MS test (day +5) and further confirmed by molecular sequencing(day +6). Trichoscopy showed black dots (purple arrows), broken hairs (blue arrows), comma hairs (red arrows), and white scales on the hair and scalp (yellow arrows) (Fig. 2C and D) (day 0). Therefore, seborrheic dermatitis-like adult tinea capitis infected by T. rubrumwas diagnosed.

Fig. 2.

Mycological and Trichoscopy examinations. (A) Direct microscopic examination. Long and separate hyphae were detected in the scaly scalp ( × 40, black arrows). (B) Fungal culture. Culture on potato dextrose agar established white and velvety colonies with red pigmentation on the surface. (C, D) Trichoscopy features of the scalp. Trichoscopy showed black dots (blue arrows), broken hairs (purple arrows), comma hairs (green arrows), and white scales on the hair and scalp (yellow arrows). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

The patient was actively advised to shave his hair, clean possible fomites, and screen family members. Nevertheless, he did not shave his hair because of aesthetic concerns. At the same time, given the age of the patient and the type of pathogen, he was treated with oral terbinafine (250 mg/day), topical ketoconazole cream (twice/day), and ketoconazole shampoo (three times/week). After a month of therapy, the patient achieved the clinical and mycological cure and showed a smooth scalp with scattered hypopigmented spots and no further hair loss (Fig. 3). The patient had no recurrence after six months of combined online and offline follow-up.

Fig. 3.

After a month of therapy, the smooth scalp with scattered hypopigmented spots was shown on the right parietal scalp.

3. Discussion

The epidemiological characteristics of ATC vary by geographic region and change with time, with prevalence ranging from 2.6% to 13.6%, which is higher than in previous decades [[3], [4], [5]]. The increasing majority of ATC may be related to population aging and immune system changes caused by systemic diseases such as diabetes, malignancy, acquired immunodeficiency diseases, or prolonged use of glucocorticoids and immunosuppressants. Interestingly, a retrospective epidemiology survey of ATC in Mainland China found that only 2.2% of patients had comorbid immunosuppressive diseases, reminding us to consider the possibility of ATC of scalp diseases among “healthy people,” especially those who have had dermatophytosis [3]. A multicenter prospective study in China found that the most common causative fungus for TC was the zoophilic Microsporum Canis (M. canis) [6]. However, compared with children, patients of ATC are more often complicated with another superficial dermatophytosis, and the proportion of anthropophilic dermatophytes is higher, including Trichophyton violaceum (T. violaceum), Trichophyton tonsurans (T. tonsurans), and T. rubrum [6].

The lesions of ATC are always atypical and various, mainly encompassing diffuse erythematous scale, black dots, abscesses, and alopecia. Generally, the inflammatory reaction was milder in anthropophilic dermatophytes but more intense in zoophilic or geophilic species. Most anthropophilic species usually appear as endothrix infections, meaning the pathogens invading the hair shaft without damaging the stratum corneum [1]. This pattern of infection is clinically characterized by black spots and scaly erythema of the scalp, which is consistent with our patient's clinical and trichoscopic features, making this case more representative.

ATC is primarily differentiated from seborrheic dermatitis and scalp psoriasis as a scalp disease. Seborrheic dermatitis usually manifests greasy scaling, itching, and erythema. It often occurs on the scalp, face, back, and chest in adults. The density of Malassezia spp has always been connected with the severity of the disease [7]. Topical antifungals are the primary treatment for this disease by reduction of the yeast [8]. Silver-white scales, well-circumscribed erythema, and hair casts characterize scalp psoriasis. Besides the scalp, psoriasis-like skin lesions are often found on the knees, elbows, and body folds [9]. Trichoscopy usually presents typical vascular patterns, such as bushy red dots and loops [10]. Mycological tests were generally negative for the disease. In addition to the above two conditions, ATC sometimes needs to be distinguished from bacterial folliculitis, alopecia areata, even lupus erythematosus, cutaneous tuberculosis, and secondary syphilis.

Generally speaking, diagnosis of ATC is made by direct microscopic detection of septate hyphae and fungal culture from scalp hair samples, but the fungal incubation usually takes 2–3 weeks [11]. MALDI-TOF MS, which is a potential alternative method of molecular sequencing for microbial identification and can enhance the test performance by expanding its database, has been proven to quickly, accurately, and economically identify bacterial, yeast, and mold species, as well as gradually applied to the identification of dermatophytes. The identification of dermatophytes by MALDI-TOF MS can be carried out at the initial stage of incubation, which is better for the early recognition of species and selection of appropriate antifungal drugs [12]. Trichoscopy, a fast, painless, and highly sensitive tool, may observe trichoscopic signs in ATC, including comma hair, broken hair, corkscrew hair, zigzag hair, and black dots, which may be peculiar to different organisms and not visualized by the naked eye [13]. Histopathological examinations are rarely conducted and used only in extremely atypical cases.

The treatment principles for ATC are similar to those for children. Both systemic and adjuvant topical antifungals are required for these patients. For oral drugs, terbinafine is usually the preferred systemic drug for infections with Trichophyton spp, while itraconazole or griseofulvin is for infections with Microsporum spp [11]. In the elderly with systemic medications, it is essential to consider underlying diseases, drug interactions, compliance, and reduce the occurrence of adverse drug events. Topical antifungal agents are necessary for reducing the transmission of spores in the initial phases of therapy [1]. Based on drug types and patients' responses, treatment duration generally ranges from 3 to 6 weeks, and mycological cure (negative microscopy and culture results) is the end point of treatment [1]. Family screening and cleaning of fomites for all anthropophilic species are vital for preventing recurrence, while identifying and treating the animal sources are also necessary for zoophilic infection.

Totally, ATC is more common in postmenopausal women, but we have reported a first misdiagnosed case of seborrheic dermatitis-like ATC caused by T.rubrum attributed to self-inoculation of superficial dermatomycosis in an elderly male who presents with scaly erythema and non-cicatricial alopecia of the scalp. The case aims to remind dermatologists and general practitioners that ATC is not a rare disease, and close contact with family members suffering from superficial fungal infections as well as autoinoculation, may be the primary mode of transmission of this disease. Increased awareness and vigilance of different clinical forms of ATC, and timely mycological examination for suspected patients, can help with early diagnosis and appropriate management.

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Handling Editor: Dr Adilia Warris

Appendix A. Supplementary data

The following are the Supplementary data to this article.

figs1.