Tinea capitis (TC) most often is caused by Trichophyton tonsurans and Microsporum canis. The peak incidence is between 3 and 7 years of age. Noninflammatory TC typically presents as fine scaling with single or multiple scaly patches of circular alopecia (grey patches); diffuse or patchy, fine, white, adherent scaling of the scalp resembling generalized dandruff with subtle hair loss; or single or multiple patches of well-demarcated areas of alopecia with fine scale studded with broken-off hairs at the scalp surface, resulting in a black dot appearance. Inflammatory variants of TC include kerion and favus.1 Herein, updates on diagnosis, treatment, and monitoring of TC are provided, as well as a discussion of changes in the fungal microbiome associated with TC. Lastly, insights to some queries that practitioners may encounter when treating children with TC are provided.
Genetic Susceptibility
Molecular techniques have identified a number of macrophage regulator, leukocyte activation and migration, and cutaneous permeability genes associated with susceptibility to TC. These findings indicate that genetically determined deficiency in adaptive immune responses may affect the predisposition to dermatophyte infections.2
Clinical Varieties of Infection
Dermatophytes causing ringworm are capable of invading the hair shafts and can simultaneously invade smooth or glabrous skin (eg, T tonsurans, Trichophyton schoenleinii, Trichophyton violaceum). Some causative dermatophytes can even penetrate the nails (eg, Trichophyton soudanense). The clinical presentation is dependent on 3 main patterns of hair invasion3:
• Ectothrix: A mid-follicular pattern of invasion with hyphae growing down to the hair bulb that commonly is caused by Microsporum species. It clinically presents with scaling and inflammation with hair shafts breaking 2 to 3 mm above the scalp level.
• Endothrix: This pattern is nonfluorescent on Wood lamp examination, and hairs often break at the scalp level (black dot type). Trichophyton tonsurans, T soudanense, Trichophyton rubrum, and T violaceum are common causes.
• Favus: In this pattern, T schoenleinii is a common cause, and hairs grow to considerable lengths above the scalp with less damage than the other patterns. The hair shafts present with characteristic air spaces, and hyphae form clusters at the level of the epidermis.
Diagnosis
Optimal treatment of TC relies on proper identification of the causative agent. Fungal culture remains the gold standard of mycologic diagnosis regardless of its delayed results, which may take up to 4 weeks for proper identification of the fungal colonies and require ample expertise to interpret the morphologic features of the grown colonies.4