Favus - Types, Causes, Clinical Features, Diagnosis, and Treatment

Introduction:

Favus or tinea favosa in Latin means “honeycomb”. Favus is a severe chronic inflammatory dermatophyte fungal infection caused by Trichophyton schoenleinii. It is a kind of tinea capitis found worldwide. Currently, it is seen in some areas of Asia and Africa. Trichophyton violaceum or Microsporum species may also cause favus. Favus is seen as yellow saucer-shaped crusts consisting of scales around hair follicles, severe hair loss, and scarring causes psychosocial problems. It may also infect the bare skin and nails.

What Are the Types of Favus?

• Tinea Capitis Favosa

  • Favus is the severe form of tinea capitis. It has a subtle course without an acute phase, leading to the diagnosis delay. In most cases, favus starts as folliculocentric erythemato-squamous areas. If these areas are removed, they progress to a cup-shaped yellow crust on the scalp with dull gray hair with underlying erythema called scutulum. As the disease progresses, many scutula fuse, covering more than one-third of the scalp. The infected hair will fall out, causing extensive permanent alopecia, atrophy, and scarring.

  • Affected skin smells with a mousy odour or cheesy. Secondary bacterial infections may cause pus formation and lymph node enlargement.

• Favus of the Bare Skin

  • Tinea favosa of the bare skin and nails are seen only in 7 % of cases. Clinically, the favus of the bare skin presents as papulovesicular and/or papulosquamous circinate eruptions with typically evident scutula. The crusts may be large and multiple, commonly affecting the scrotum. Skin atrophy may be observed in affected areas.

• Onychomycosis Favosa

  • 2.4 % of cases of favus showed nail involvement. Individuals are infected when they accidentally hurt their fingernails when epilating an infected scalp. Favus of fingernails was the major source of scalp reinfection when patients were treated by radiotherapy.

• Generalized Favus

  • Generalized favus is rare, representing only 0.1 % of tinea favosa cases. It is seen in poor and rural areas. Clinical presentations include mucous involvement, esophagitis, gastroenteritis, keratitis, and endophthalmitis.

• Atypical Presentation

  • Atypical scutula favus includes pityroid, impetiginous, follicular, papyroid, and psoriasiform forms without alopecia. The atypical presentations have a delayed diagnosis and treatment.

Some other forms of favus are:

• Favus pityroides: Mimics dandruff or seborrhoeic dermatitis.

• Favus papyroides: Small spot on the scalp covered by a delicate substance.

• Favus psoriasiformis: Psoriasis-imitating favus.

• Favus impetigoides: Yellow crusts that imitate impetigo lesions.

• Favus follicularis: Cone-shaped wax-colored bumps around the hair follicles.

• Favus herpetiformis: Round, red, scaling plaques with small papules, pustles, vesicles, and crusts found on the trunk and extremities.

What Causes Favus?

Trichophyton schoenleinii is the cause of 95 % of favus cases.

Rarely occurring species include:

• Zoophilic species - Microsporum canis, Trichophyton mentagrophytes and Trichophyton verrucosum.

• Geophilic species - Microsporum gypseum.

• Anthropophilic species - Trichophyton violaceum.

Who Does Favus Affect?

Favus affects both males and females of all age groups. But the higher incidence is seen in the following groups.

• Boys - Shorter hair allows easy entry for circulating spores.

• Menopausal women - As the blood estrogen levels decrease, sebaceous glands shrink.

What Are the Clinical Features of Favus?

Favus is characterized by yellow cup-shaped crusts (scutula) that group together, forming a honeycomb pattern. Each crust surrounds a hair strand, which pierces the center and pokes out. There are three stages in favus based on its severity.

They are,

• Stage 1: Red and inflamed areas around the hair follicles on the scalp. Hair stays intact.

• Stage 2: Yellow cup-shaped crusts (scutula) and hair start to fall out.

• Stage 3: One-third of the scalp is affected with widespread hair loss, atrophy, and scarring.

The scutula forms dense plaques that often harbor secondary bacterial infection. Removal of the plaques leaves a red, swollen, moist base.

What Is the Test to Diagnose Favus?

Favus is diagnosed with the following tests:

1. Skin scraping.

2. Direct microscopic examination.

3. Fungal culture.

4. Polymerase Chain Reaction (PCR) test is an alternate test when fungal culture is unsuccessful.

How Is Favus Treated?

Favus treatment involves oral, topical antifungal agents and local therapies.

• Systemic Treatment:

  • Griseofulvin is effective for Trichophyton schoenleinii infection. Oral Terbinafine, Itraconazole or Fluconazole is also prescribed. Due to the carcinogenicity and teratogenicity of Griseofulvin, newer antifungal drugs like Terbinafine and Azoles are recommended.

• Topical Agents:

  • Additionally, topical agents like 2% Ketoconazole or Isoconazole and 2.5% Selenium sulfide shampoos may be helpful. These shampoos, foam gel, lotion, and spray are applied twice a day.

• Local Treatment:

  • Remove the debris and crusts from the scalp and clean the scalp regularly.

  • Cut off hair around the alopecia patches.

  • Nail involvement requires more prolonged therapy.

Repeated negative fungal cultures confirm the success of therapy.

What Is the Differential Diagnosis of Favus?

The differential diagnosis of scalp favus is similar to that of tinea capitis. Similar other lesions include:

• Amiantacea tinea - Is a red and itchy scalp in which a thick, adherent scale infiltrates and surrounds the base of scalp hairs.

• Kerion celsi - An acute inflammatory process caused by the host response to a fungal ringworm infection of the hair follicles of the scalp.

• Impetigo - Bacterial infection affecting the superficial skin.

• Sarcoidosis - A disease characterized by the growth of small collections of inflammatory cells in any part of the body.

• Squamous cell carcinoma involving the skin.

• Seborrheic dermatitis – Not seen in children before puberty.

• Psoriasis is not common in children, in whom favus is most prevalent; psoriasis involves the occipital scalp and/or other skin or nail involvement.

• Atopic dermatitis is a universal disorder involving the flexural body parts in school children.

• Lichen planopilaris – An unusual condition causing scarring alopecia, associated with lichen planus on areas of the skin or mucosa.

• Discoid lupus erythematosus – An extremely unusual condition in children involving areas of the head and neck and associated with sun sensitivity.

• Folliculitis decalvans – A form of purulent scarring.

• Central centrifugal cicatricial alopecia – A form of scarring alopecia most common in middle-aged women with a history of chemical or thermal hair straightening.

What Are the Risk Factors for Favus?

The risk factors of favus include:

• Sharing towels, clothing, combs, and hairbrushes from infected persons.

• Poverty.

• Poor hygiene and malnutrition.

• Little access to health care.

• Overcrowding.

• Immunocompromised patients.

• Virulence of the specific dermatophyte.

What Are the Complications of Favus?

• Permanent alopecia.

• Stigmatization.

• Disfigurement.

• Side effects of treatment.

• Social withdrawal.

• Psychological impairment in children.

Conclusion:

Favus is a severe clinical type of tinea capitis. It is a chronic mutilating disease with profound familial and social implications. The treatment outcome varies depending on the stage at which the condition is diagnosed. With early diagnosis and proper therapeutic management, favus can be cured without consequences. However, late treatment leads to the ultimate scarring hair loss in all clinical presentations.