Edit concept Create issue ticket

Tinea Favosa

Tinea favosa is a persistent infection of the scalp, caused by a type of fungus called dermatophytes.


Presentation

The first and primary site of a favus infection is usually the scalp. Initially, hair remains intact but develops a reddish, erythematous appearance. As the infection remains untreated, scutula begin to appear: yellow, diamond or disc-shaped crusts that form a structure that resembles a honeycomb. Scutula are not only the result of the already existing infection: they are a substrate onto which re-infection can occur and may extend to the entire scalp in extreme cases. At its most severe and progressed stage, favus leads to alopecia in the affected regions, which can unfortunately not be reversed. The skin becomes atrophic and scarred. Skin that typically contains no hair can also be infected by T. schoenleinii. Scutula may be observed, alongside papulovesicular eruption.

There is a wide variety of favus types that extend beyond the typical aforementioned clinical manifestations:

  • Favus pityroides: It can be misdiagnosed as dandruff, due to the presence of scales.
  • Favus follicularis: It resembles favus, but is accompanied by papules which form in the skin adjacent to the hair follicles.
  • Favus papyroides: The scutula, that may or may not be present, are enveloped by lesions whose appearance resembles that of a parchment.
  • Favus psoriasiformis: This type of favus very closely resembles the appearance of psoriasis.
  • Favus herpetiformis: It affects the trunk and limbs. This type of favus leads to the formation of reddish, circular lesions, accompanied by pustules or vesicles.

The scalp of patients affected by tinea favosa emits an obnoxious smell that resembles that of a mouse. It is important to bear in mind that, if diagnosed early, tinea favosa is curable, and no permanent damage to hair follicles is sustained. A delay in diagnosis and treatment leads to extensive infection and permanent alopecia. It is believed that almost all cases of favus have, in the past, reached the stage of irreversible hair loss.

Workup

For a definitive diagnosis to be obtained, hair needs to be examined for the presence of fungi.

Direct microscopy can help to illustrate fungal presence. A KOH solution must be used to achieve better image clarity. A typical characteristic is that the immediate examination in a KOH solution reveals air spaces between the fungal hyphae, due to their autolytic tendency. A culture will give the final diagnosis of the causative agent; the preferred substrate is the Sabouraud agar with chloramphenicol, in order to hinder other fungi or bacteria from growing on it. In general, the more the disease has progressed, the more difficult it is to obtain a diagnostic culture.

A biopsy can also be carried out if suspicion of tinea favosa exists. Histology is expected to show scutula filled with mycelium and hyphae, accompanied by mild inflammation.

Patients' sera contain antibodies, which can be detected but are of uncertain purpose and diagnostic value [8].

Treatment

Favus is an infection caused by the dermatophyte T. schoenleinii. The pathogen may be transmitted to humans from other people, from animals or infected objects. It is generally believed that person-to-person transmission is not particularly common; however, once a member of a family is diagnosed with favus, all other members must receive treatment as well.

Treatment follows a double-action plan: local application of shampoos and creams further enhances the efficacy of the antifungal medications. Specifically, the infected area must be cleaned from scutula, the patient should be encouraged to maintain higher hygienic standards and a shampoo containing 2% ketoconazole and 2.5% selenium sulfide can be used.

The antifungal drug that has been proven effective against favus is griseofulvin; although T. schoenleinii is sensitive to more state-of-the-art antifungal medications, its declining incidence has lead to no substantial clinical evidence that it can be used to cure the infection. Nevertheless, the following medications can be theoretically administered in order to cure favus and prevent permanent scarring and disfigurement:

  • Itraconazole: inhibitor of the synthesis of ergosterol, which is dependent on the P-450 cytochrome. Ergosterol is necessary for the solidification of the membrane of the fungus.
  • Terbinafine: indirectly inhibits the production of ergosterol.
  • Fluconazole: another P-450 cytochrome inhibitor.

Griseofulvin, the drug administered until now against favus, attaches itself to keratin precursor cells. It is prescribed at a dosage of 15-20 mg per kilogram of body mass per day for a long period of time, approximately for twelve weeks.

Prognosis

Favus is characterized by a poor prognosis, as far as a spontaneous resolution is concerned. The infection is durable and fungi may thrive for many years, which typically leads to extensive scarring and irreversible loss of hair.

Etiology

Tinea favosa is a fungal infection, characterized by chronicity and persistence, that is primarily caused by dermatophytes, and particularly Trichophyton schoenleinii [5] [6]. Other than this specific fungus, other fungi classified under the Microsporum and Trichophyton genera can cause this infection, but the vast majority of the cases seem to be a result of a T. schoenleinii infestation.

T. schoenleinii is a fungus that may be carried by animals, humans or even objects that may be infested with it. Poor hygienic conditions and lack of information had previously led to tinea favosa being an infection endemic to Africa. Presently, this type of infection is rare, even in those regions.

Epidemiology

Tinea favosa is an infection primarily observed in impoverished or underdeveloped regions, due to the insufficient information available concerning personal hygiene or negligence. It has been an infection endemic to parts of the world such as Africa, Southern China, the Middle East; some cases have nevertheless been reported in rural areas of the United States, Australia, Britain, and Canada [7].

Favus doesn't follow a gender-related or ethnic susceptibility and is an infection that firstly occurs during childhood and typically prevails for many years.

Sex distribution
Age distribution

Pathophysiology

Favus is a scalp and glabrous skin infection, mostly caused by the dermatophyte T. schoenleinii. Hair is moderately infected and still grows in some cases. Clinically, it induces the formation of scutula, namely disc-shaped yellow lesions that can be sometimes followed by alopecia.

Apart from the scalp, the infection can also be observed on the nails and the bearded region of the face; this clinical variant is, however, not particularly common. Microsporum canis, Trichophyton verrucosum, and Trichophyton violaceum are some of the other agents that can cause tinea favosa as well.

Prevention

The incidence of tinea favosa is directly related to an individual's living standards. Poverty, inadequate coverage of basic dietary needs and a poor personal hygiene can lead to the acquisition of such an infection.

Summary

Tinea favosa otherwise referred to as favus, is a persistent fungal infection of the scalp. Trichophyton schoenleinii is the most common culprit behind the infection and leads to a characteristic, disc-like appearance of the scalp and/or skin that is normally free of hair [1]. The chronicity of the infection progressively leads to inflammation, loss of hair (alopecia) and an infection that may extend to the nails as well.

The incidence of the infection used to be particularly high in regions of Africa, such as Tunisia. During the last years, its frequency has been declining, but the two regions where the microorganism is mainly observed are still Africa and Eurasia. Apart from the predominant clinical presentation that involves disk-shaped lesions (scutula) and alopecia, the same infection can sometimes lead to completely atypical clinical manifestations [2] [3].

Other dermatophytes that can cause tinea favosa are Trichophyton mentagrophytes var quinckeanum, Microsporum gypseum and other microorganisms [4].

Tinea favosa is diagnosed via microscopic analysis of a patient's hair. Histology can sometimes corroborate the positive result. The treatment that is considered first-choice is the fungistatic griseofulvin, which has not been replaced by newer medications, due to a lack of clinical trials to determine their efficacy against T. schoenleinii.

Patient Information

Tinea favosa is an infection caused by fungi. Although a variety of different microbes can cause this particular infection, the vast majority are a result of infestation with Trichophyton Schoenleinii, a fungus that belongs to the dermatophytes genre.

Tinea favosa is otherwise known as favus. The infection usually starts on the scalp and may extend to nearby regions that normally contain no hair, or even to the nails. The scalp acquires a reddish erythematous appearance and ,in time, a "honeycomb-like" appearance, due to the formation of scutula, namely areas shaped like discs, that are covered by a yellow crust. If the infection is not treated in time, the infected areas lose their hair, due to the inflammation and the hair will never grow back again.

Favus is rare in the industrialized world; it has been a type of infection commonly seen in regions of Africa, rural China and, generally, in regions that are underdeveloped or impoverished, although sporadic cases have been reported in rural parts of the USA and England. Failure to adhere to basic hygienic standards is the primary cause of an increased frequency in favus. During the past years, the number of people affected by the infection has been steadily declining. The infection is diagnosed via microscopic examination of a person's hairs and a culture, which will illustrate the exact type of microorganism that has caused it.

Favus is a curable infection but it is necessary to diagnose it as early as possible in order to avoid permanent hair loss from a neglected, progressed infection. The drug used to cure it is called griseofulvin: it is an old antifungal medication which has proven to be effective against Trichophyton schoenleinii and it still the first choice of treatment, even though newer medications against fungi have emerged. Additionally, patients are encouraged to use special shampoos, creams and lotions in order to remove the crusts. They are also asked to maintain better standards of hygiene to prevent a new infection.

References

Article

  1. Cecchi R, Paoli S, Giomi A, Rossetti R. Favus due to Trichophyton schoenleinii in a patient with metastatic bronchial carcinoma. Br J Dermatol. 2003;148(5):1057.
  2. Ilkit M. Favus of the scalp: an overview and update. Mycopathologia. 2010;170(3):143-54.
  3. Khaled A, Ben Mbarek L, Kharfi M,et al. Tinea capitis favosa due to Trichophyton schoenleinii. Acta Dermatovenerol Alp Pannonica Adriat. 2007;16(1):34-6.
  4. Garcia-Sanchez MS, Pereiro M Jr, Pereiro MM, Toribio J. Favus due to Trichophyton mentagrophytes var. quinckeanum. Dermatology. 1997;194(2):177-9.
  5. Zaraa I, Hawilo A, Aounallah A, et al. Inflammatory Tinea capitis: a 12-year study and a review of the literature. Mycoses. 2013;56(2):110-6.
  6. Matte SM, Lopes JO, Melo IS, Beber AA. A focus of favus due to Trichophyton schoenleinii in Rio Grande do Sul, Brasil. Rev Inst Med Trop Sao Paulo. 1997;39(1):1-3.
  7. Loveman AB, Kotcher E. Favus in Kentucky: diagnosis, treatment and epidemiology. J Ky Med Assoc. 1962;60:643-55.
  8. Grappel SF, Blank F, Bishop CT. Circulating antibodies in human favus. Dermatologica. 1971;143(5):271-6.

Ask Question

5000 Characters left Format the text using: # Heading, **bold**, _italic_. HTML code is not allowed.
By publishing this question you agree to the TOS and Privacy policy.
• Use a precise title for your question.
• Ask a specific question and provide age, sex, symptoms, type and duration of treatment.
• Respect your own and other people's privacy, never post full names or contact information.
• Inappropriate questions will be deleted.
• In urgent cases contact a physician, visit a hospital or call an emergency service!
Last updated: 2017-08-09 17:22