Author: Assoc Prof Patrick Emanuel, Dermatopathologist, Auckland, New Zealand, 2013.
Dermatophytic infections of the scalp (tinea capitis) are characterized by involvement of the hair shaft by pathogenic fungi.
Histology of tinea capitis
The causative organism determines the pattern of hair invasion.
Endothrix infections – There is minimal epidermal response aside from mild hyperkeratosis (figure 1). The hyphae extend within the hair shaft and produce spores (figures 2, 3). This form is caused by Trichophyton tonsurans/violaceum.
Ectothrix infections – There is also often minimal inflammatory reaction. The fungal forms coat the outside of the hair shaft without significant invasion of the shaft itself. This is typically caused by Microsporum canis/audouinii.