Monday, 25 October 2010

Favus

Favus. Trichophyton Schoenleinii infection. Latin: favus, honeycomb (note that kerion, a different form of tinea capitis/barbae, also means honeycomb but in Greek).

Hair invasion results in favus endothrix pattern. The fungus is entirely confined within the hair shaft but does NOT fragment into arthroconidia (thus the infected hair commonly grows to normal lengths). Actually the relatively few hyphae run intact through the hair, forming tunnels within its structure. When first immersed in KOH, air is initially trapped around the hyphae forming the characteristic, long air spaces. These rapidly fill in with KOH, when the hyphae themselves become visible.

The classical picture of tinea capitis caused by this organism is characterized by the presence of yellowish cup-shaped crusts known as scutula. Adjacent crusts enlarge to become confluent and form a mass of yellow crusting (with unpleasant odour). Having said so, there might be less distinctive changes in the early cases (perifollicular redness and some matting of the hair). Seborrhoeic dermatitis with or without alopecia areata, pityriasis amiantacea, psoriasis and impetigo are considered in the differential diagnosis. Scalp demodicidosis mimicking favus has been reported*.

Trichophyton schoenleinii causes a pale green fluorescence of infected hair under Wood’s light. Because fungi growing in culture or on hair in vitro do not fluoresce in this way, the phenomenon must be attributed to some substance (? a pteridine) produced by the interaction of the fungus and the growing hair.

Extensive, patchy hair loss with cicatricial alopecia and atrophy among patches of normal hair may be found in long-standing cases, where much of the hair loss is irreversible. Discoid lupus erythematosus, lichen planus and other causes of cicatricial alopecia are considered in the differential diagnosis.


Favus appears chiefly on the scalp but may affect the glabrous skin and nails. When infected the glabrous skin develops similar yellowish crusts. T. schoenleinii nail invasion (up to 3% of infections) is indistinguishable from other causes of onychomycosis. T. violaceum and M. gypseum infection can produce a favus-like clinical picture. It is interesting to note that favus among the Bantus in South Africa is called witkop (in Afrikaans it means “the white head”). Tinea capitis in general is predominantly an infection of children, although adult cases are occasionally seen. Favus in particular, shows little if any tendency to clear spontaneously at puberty. Tinea capitis may also be seen in adults with AIDS.

Ketoconazole shampoo or selenium sulphide shampoo is helpful to prevent spread in the early phases of therapy, when used in combination with an oral treatment [higher dosage of griseofulvin (20 mg/kg/day) for much longer course may be needed].

*García-Vargas A, Mayorga-Rodríguez JA, Sandoval-Tress C. Scalp demodicidosis mimicking favus in a 6-year-old boy. J Am Acad Dermato. 2007; 57, suppl. 2: S19-S21.

1 comment:

  1. NB Tinea capitis is treated systemically; additional topical application of an antifungal may reduce transmission. Griseofulvin is used for tinea capitis in children and adults. Terbinafine is an alternative for certain infections such as those caused by Trichophyton species. The role of terbinafine in the management of Microsporum infections is uncertain. Fluconazole or itraconazole are alternatives in the treatment of tinea capitis. The appropriate length of treatment with either itraconazole or fluconazole is not established.

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Main Works of Reference List (The first eight are my top favourites)

  • British National Formulary
  • British National Formulary for Children
  • Guidelines (BAD - BASHH - BHIVA - Uroweb)
  • Oxford Handbook of Genitourinary Medicine, HIV, and Sexual Health
  • Oxford Handbook of Medical Dermatology
  • Rook's Textbook of Dermatology
  • Simple Skin Surgery
  • Weedon's Skin Pathology
  • A Concise Atlas of Dermatopathology (P Mckee)
  • Ackerman's Resolving Quandaries in Dermatology, Pathology and Dermatopathology
  • Andrews' Diseases of the Skin
  • Andrology (Nieschlag E FRCP, Behre M and Nieschlag S)
  • Bailey and Love's Short Practice of Surgery
  • Davidson's Essentials of Medicine
  • Davidson's Principles and Practice of Medicine
  • Fitzpatrick's Colour Atlas and Synopsis of Clinical Dermatology (Klaus Wolff FRCP and Richard Allen Johnson)
  • Fitzpatrick’s Dermatology in General Medicine
  • Ganong's Review of Medical Physiology
  • Gray's Anatomy
  • Hamilton Bailey's Demonstrations of Physical Signs in Clinical Surgery
  • Hutchison's Clinical Methods
  • Lever's Histopathology of the Skin
  • Lever's Histopathology of the Skin (Atlas and Synopsis)
  • Macleod's Clinical Examination
  • Martindale: The Complete Drug Reference
  • Oxford Handbook of Clinical Examination and Practical Skills
  • Oxford Textbook of Medicine
  • Practical Dermatopathology (R Rapini)
  • Sexually Transmitted Diseases (Holmes K et al)
  • Statistics in Clinical Practice (D Coggon FRCP)
  • Stockley's Drug Interactions
  • Treatment of Skin Disease: Comprehensive Therapeutic Strategies
  • Yen & Jaffe's Reproductive Endocrinology