Introduction

Tinea capitis (TC) is a dermatophyte infection of the scalp and hair that appears most common in children, especially preschool children between 3 and 7 years old [1]. It rarely occurs in children in their first two years of life, and there are only a few literatures reporting this age group population and most of them are case reports [2, 3]. Therefore, the epidemiological, clinical and mycological characteristics of pediatric TC in children less than two years old are still unknown. Clinically, pediatric TC can vary considerably, including scaling, annular erythema, alopecia, broken hairs or even kerion, which often leads to misdiagnosis, such as seborrheic dermatitis, neonatal lupus erythematosus, impetigo or atopic dermatitis [4, 5]. If the diagnosis and treatment are not timely, it will cause serious consequences, and even permanent hair loss. Systemic antifungal therapy is the standard for TC, however, for a majority of countries there has been no Food and Drug Administration (FDA) approved oral drugs for the children under two years old [6]. In addition, there is still a lack of research or guidelines for what kind of therapy should be recommended in this age group, which limits clinical treatment. In this study, we systematically reviewed all literatures and summarized the epidemiology, clinical features, pathogens and treatment strategies of TC in children younger than two years old, in order to provide effective information and recommendations on the treatment for clinicians.

Methods

We reviewed all cases in children less than two years of age with an established diagnosis of TC from 1991 to 2022 (32 years), using the key search terms (“tinea capitis” OR “kerion” OR “favus”) AND (“children” OR “infant” OR “newborn” OR “neonate” OR “pediatric” OR “younger than two years old”). A search for all studies (case reports, case series, retrospective or prospective trials) were performed in the following foreign and domestic databases: PubMed, Embase, Web of Science, CNKI (http://www.cnki.net/), WanFang (http://www.wanfangdata.com.cn/) and WeiPu (http://www.cqvip.com/). Titles and abstracts from initial search were reviewed. Inclusion criteria were as follows: (i) studies published in either English or Chinese; (ii) articles published from 1991 to 2022; (iii) included patients’ age under 2 years old; (vi) established diagnosis of TC. The remaining studies were reviewed in detail and studies with obvious wrong or unclear records of data were excluded. Data on demographics, source of contagion, clinical presentation, pathogen, treatment, drug safety and prognosis were extracted from qualified studies and were analyzed using descriptive statistics.

Results

A total of 651 articles were retrieved by using the key search terms, and 47 articles were qualified according to the inclusion and exclusion criteria. One hundred and twenty-six cases of TC in children less than 2 years old from 14 countries were included and analyzed (Tables 1 and 2).

Table 1 Data on demographics, source of contagion, clinical presentation and pathogen of tinea capitis in children younger than two years old
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Table 2 Data on treatment, drug safety and prognosis of tinea capitis in children younger than two years old
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Epidemiological Features

Males (68 cases, 56.20%) of pediatric TC were slightly higher than females (53 cases, 43.80%) with a sex ratio (M/F) of 1.28:1. The other nine patients’ gender information were not available in the literatures. The patients’ age ranged from 10 days old to 2 years old with a median age of 3 months, among them, children younger than 6 months old accounted for the highest proportion of 46.03% (Fig. 1). The duration of the disease prior to diagnosis ranged from 3 to 270 days (median = 30 days). A total of 30 cases (23.8%) had a clear history of misdiagnosis as seborrheic dermatitis, eczema, impetigo or neonatal lupus, treated with topical steroid cream (13 cases) and systemic or topical antibiotics (12 cases), which aggravated the lesions and even evolved into kerion. Animals (35 cases, 27.78%) were the most common source of contagion, followed by humans (31 cases), accounting for 24.60% (Fig. 2).

Fig. 1
figure 1

Age distribution of tinea capitis in children younger than two years old

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Fig. 2
figure 2

Source of contagion of tinea capitis in children less than two years old

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Clinical Manifestations and Pathogens

The clinical presentation of pediatric TC was variable, and the main clinical manifestations were alopecic patches (40 cases, 31.7%) and scaling (39 cases, 31.0%) on the scalp. Twenty-nine children (23.0%) appeared follicular pustules with exudative or overlying crust on alopecic patches, suggesting a kerion. Four cases (3.17%) and one case (0.79%) were diagnosed as black-dot tinea and favus due to T. mentagrophytes var. quinckeanum, respectively. The other thirteen patients’ clinical manifestations were not described in detail. There were 12 species of dermatophytes isolated from patients. The most predominate pathogens were M. canis (64 cases, 50.79%), followed by T. violaceum (13 cases, 10.32%), T. mentagrophytes complex (12 cases, 9.52%) and T. tonsurans (10 cases, 7.94%). Other strains were only reported in several cases, besides, a case of TC in a newborn was found caused by two organisms, T. rubrum and T. mentagrophytes complex (Fig. 3).

Fig. 3
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The pathogenic organisms of tinea capitis in children under two years old

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Treatment and Prognosis

Ninety-five children (75.4%) were treated with systemic antifungal drugs, including 64 patients with griseofulvin, 13 patients with itraconazole, 8 patients with terbinafine, 7 patients with fluconazole, and 3 patients with two oral antifungal drugs for the former one ineffective. Besides, 22 patients (17.46%) were only treated with topical therapy, and 9 patients’ treatment strategy were unknown (Fig. 4). Except for 10 patients with unknown final prognosis, all the other cases were cured after treatment and one patient relapsed after treatment with griseofulvin 20 mg/kg/d for two months, who was cured after giving griseofulvin for another one month. There were almost no drug-related side effects except one child (0.79%) presented with gastrointestinal symptoms from griseofulvin, who got better after stopping the drug.

Fig. 4
figure 4

Treatment strategies of tinea capitis in children in their first two years of life

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Discussion

We systemically reviewed all articles published in English and Chinese referring to TC in children less than two years old. This study revealed the epidemiological features and treatment recommendations of pediatric TC, providing valuable information for the diagnosis and treatment of TC in children under two years old.

Overall, the data on TC in this age group are limited because of the unusual and low reported prevalence. Children aged 3 ~ 7 years old remain the most commonly affected [1]. We found that the epidemiology, pathogen spectrum and clinical presentation of TC in children younger than two years old were similar to those older than two years old [50], and different from TC in adults [51]. In infants and children, boys were slightly more susceptible to TC than girls (1.28:1), which may be attributed to boys having short hair, more contact with animals and more outdoor physical activities [52]. We confirmed that the top four pathogens were M. canis, T. violaceum, T. mentagrophytes complex and T. tonsurans. The most common zoophilic species were M. canis, followed by T. mentagrophytes complex, which can cause dermatophytosis in animals, and indirectly infect humans through close contact [53]. The most commonly isolated anthropophilic dermatophytes were T. violaceum and T. tonsurans, and mothers were the main source of contagion, who acted as symptomatic or asymptomatic carriers of the anthropophilic pathogens. TC may be seen in various clinical presentation, including hair loss, scaling, black dots, follicular pustules and kerions, depending on the species of dermatophytes, the phase of infection and the immune status of the host [54]. The symptoms of TC in children younger than two years old were similar to older children, and alopecic patches and scaling were noted as the most common types. Therefore, the diagnosis of TC should be considered when an infant presents with scaling, alopecic patches or broken hair on the scalp [23].

Historical data revealed that the fungal distribution pattern of TC in children varied in different countries and times [55]. In China, with the development of economy, the improvement of sanitation and social changes, zoophilic fungi (M. canis) are gradually replacing anthropophilic fungi (T. schoenleinii and T. violaceum) as the most prevalent agent of TC [56]. In Central Europe and the Mediterranean countries, pets are becoming the most likely sources of contagion and TC is predominantly due to M.canis [57]. Whereas in the USA, France and the UK, due to the increase in the immigration of people with African origin, most cases of TC are caused by T. tonsurans [58, 59]. In some Africa areas, TC has always been a serious problem for the poor hygiene and socioeconomic conditions, and dermatophytes with partial geographical restriction, like T. violaceum and T. soudanense, were the leading pathogens [60, 61]. In our study, for the limited cases of TC in younger children, we didn’t find the significant differences in fungal profiles across countries and regions.

Clinically, systemic antifungal drugs have always been recommended for the successful treatment of TC. Since 1959, griseofulvin remains the gold standard of systemic therapy for TC, but high doses and long treatment periods are warranted [62]. The newer antifungal agents terbinafine, itraconazole and fluconazole are now being used more frequently for TC especially in children older than 2 years old, with good efficacy and safety but a reduced treatment duration [6, 63]. However, for the majority of countries in the world, there are still no FDA approved oral agents or treatment guidelines of TC for the children less than two years of age [64]. Till now, there is controversy on whether systemic or topical treatment should be used for TC in this age group. There are mainly two sides of cautious. For one hand, systemic therapy is an off-label treatment, and drug risks limit the use of oral drugs. For the other hand, although topical therapy is felt to be safer for infants, TC usually causes infection at the root of the hair follicle deep within the dermis, and topical treatment alone cannot completely clear the fungus, resulting in higher recurrence rates. In our literature review, we noted that both oral and topical drugs have achieved good therapeutic effects, and almost no reported side effects and recurrence were noted during the whole treatment period and follow up. Besides, Chen et al. [65] found that oral itraconazole was safe and effective in infants and the profiles of adverse events were similar to those in adults and older children through a retrospective analysis of a large number of articles. These results remind us oral antifungal drugs, including griseofulvin, itraconazole, terbinafine and fluconazole, have few adverse effects and topical treatment can be an alternative choice, furthermore, the issues of drug safety and recurrence are not as many as we worried about.

Here, we give the following treatment recommendation for pediatric TC in children under two years old according to these acquired data: (i) children with consent of the guardian or severe clinical symptoms, treatment with systemic antifungal drugs should be recommended, and adverse reactions can be monitored; (ii) infants, especially neonates, with mild symptoms, underlying diseases or no agreement of their guardian, topical therapy should be considered; (iii) the combination of topical and systemic treatment for severe patients might increase the cure rate and shorten the duration of systemic antifungal drugs; (vi) topical cream and antimycotic shampoo can be applied to reduce the transmission of infection and to decrease shedding of infected fungal elements [4].

In this study, we systematically summarized the epidemiological, clinical and pathogenic characteristics of TC in children less than two years old, and based on these data analysis, we gave the treatment recommendation. Oral treatment for pediatric TC were safe, and topical therapy can be an alternative choice, achieving good therapeutic effects. In sum, it is of great significance to improve the treatment for pediatric TC in younger children.