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Favus: causes, symptoms, diagnosis, treatment
Last reviewed: 07.07.2025
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Favus is a rare chronic fungal disease that affects the scalp, long and vellus hair, smooth skin, nails and internal organs.
Causes and pathogenesis of favus. The causative agent of the disease is Trichophyton schonleinii. The source of infection is a person and items of his clothing. Contagiousness is low, but long-term family and household foci may arise. Most often, the infection is transmitted through the female line.
Symptoms of favus. On the scalp, there are cuticular, squamous (pityrioid) and impetiginous forms of favus of the scalp. The first form is typical for favus, the second two are atypical.
The scutular form is an ochre-yellow crust (scutula) with a saucer-shaped depression in the center. When the crust is removed, atrophy or scars are found. In most patients, the scutula are penetrated by dry hair that has lost its shine and elasticity, resembling tow. There is no lesion along the edge of the scalp (if the entire head is affected). A specific "mousey", "barn" smell from the patient's head is characteristic.
In the squamous (pityrioid) form, diffuse lamellar peeling is observed, resembling pronounced seborrhea. Atrophic changes in the scalp are visible under the scales.
The impetiginous form is characterized by the predominance of yellow-brown crusts and is very similar to vulgar impetigo or an eczematous process complicated by a secondary infection.
After removing the crusts, atrophic changes in the scalp are also visible. The hair changes are the same as in other forms of favus.
Skin lesions are manifested by the formation of hyperemic and flaky lesions in addition to cutules, which resembles trichophytosis of smooth skin.
The most characteristic feature of favus is the slow involvement of the nail plate in the process. Only the fingernails are affected. A brown or dirty-gray spot appears in the center of the nail plate, which exists for a very long time and, gradually expanding, captures the entire nail plate - subungual hyperkeratosis develops. Over time, the nails begin to crumble, but less than with other onychomycosis.
Secondary rashes can be superficial (lichenoid, erythematous, erythematosquamous) and deeper (nodular, subcutaneous). It is rare to find fungal elements in them.
Lesions of internal organs (lungs, gastrointestinal tract, favosal lymphadenitis, favosal meningoencephalitis) are observed in weakened, exhausted patients, as well as those suffering from tuberculosis infection. In these cases, the pathogen is searched for in sputum, feces, cerebrospinal fluid and the ATS lymph nodes.
The diagnosis is made based on the detection of scutulae, cicatricial atrophy with baldness and the presence of healthy hair at the periphery.
Differential diagnosis. The disease is differentiated from trichophytosis, microsporia, Broca's pseudopelade, streptoderma, psoriasis, eczema, etc.
Treatment of favus. The same treatment measures are carried out as for trochophytosis.
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