Favus - Hair and Scalp
While favus used to occur worldwide, vast improvements in socioeconomic conditions have limited it to areas where the population suffers from poor hygiene and malnutrition. Currently, favus is mostly seen in Africa, some parts of Asia and the Middle East, and some parts of Eastern Europe; it is rarely encountered in the United States or Western Europe. Typically, scalp favus is acquired during childhood through close contact with other affected individuals. Combs and hairbrushes remain an important source of infection.
Scalp favus presents first as erythematous papules surrounding intact hair follicles. The papules become more inflamed and eventually develop characteristic thick, yellow-brown crusts composed of hyphae and keratin debris, resembling a honeycomb. T schoenleinii is an endothrix (residing within the hair shaft), and it destroys the hair shaft, eventuating in hair loss. Left untreated, concave, cup-shaped debris (termed scutula) steadily engulf ever more hair, leading to a progressive scarring alopecia.
B35.9 – Dermatophytosis, unspecified
85375000 – Tinea favosa
Differential Diagnosis & Pitfalls
- Seborrheic dermatitis – Not typically seen in children before puberty, as they lack the appropriate cytokine milieu to develop this condition.
- Psoriasis – Not common in children, in whom favus is most pervasive; psoriasis also tends to involve preferentially the occipital scalp and/or have other skin or nail involvement to suggest the disease.
- Atopic dermatitis – A pervasive disorder that in school-aged children typically also involves the flexural areas of the body, such as the antecubital and popliteal areas.
- Lichen planopilaris – An unusual condition and cause of scarring alopecia, often associated with lichen planus on other areas of the skin or mucosa.
- Discoid lupus erythematosus – An extremely unusual condition in children, it also involves other areas of the head and neck, such as the conchal bowls, and is associated with sun sensitivity.
- Folliculitis decalvans – A form of purulent scarring alopecia that is unusual in children of the age typically affected by favus.
- Central centrifugal cicatricial alopecia – A form of scarring alopecia most common in middle-aged women, usually in those individuals with an extensive history of chemical or thermal straightening of the hair.