What is Favus?
Favus, or tinea favosa, is a severe, long-term skin infection mostly caused by a type of fungus called Trichophyton schoenleinii. The term ‘favus’ originated in the early 19th century, and initially referred to the honey-like substance seen in some scalp infections. In 1839, the fungus behind this condition was identified by Johann Lucas Schoenlein. This severe form of scalp infection was once very common, especially in poorer countries. Nowadays, it’s mostly seen in certain regions in Asia and Africa.
Symptoms of favus include yellow, bowl-shaped crusts around the hair follicles (referred to as scutula) and severe scarring hair loss, which can cause significant distress and social problems. Other than the scalp, the infection can also affect skin areas without hair and the nails.
What Causes Favus?
Favus, a kind of fungal infection, is mainly caused by a fungus called Trichophyton schoenleinii, which is responsible for about 95% of the cases. Sometimes, though, other types of fungi can cause favus too. These can include fungi that generally live on animals (like Microsporum canis, Trichophyton mentagrophytes var quinckeanum, and Trichophyton verrucosum), fungi that live in soil (like Microsporum gypseum), and other fungi that live on humans (like Trichophyton violaceum).
Favus spreads in a couple of ways. First, it can spread indirectly from small bits of hair or skin cells that have the fungus on them. Second, it can spread from direct contact with someone who has it, like a family member or close friend. Sharing items like towels, clothes, barber tools, or hairbrushes can also spread the fungus.
There are a few classes of people who are at a higher risk of getting favus:
– People with weakened immune systems
– Those exposed to particularly virulent strains of the fungus (specifically strains that produce keratinolytic proteases, which are proteins that help the fungus break down skin)
– People with poor hygiene and malnutrition
– People living in overcrowded conditions
– People living in poverty
– People with limited access to healthcare.
Risk Factors and Frequency for Favus
Favus, an infectious disease, was widespread in various parts of the world like southern Africa, Mediterranean areas, Pakistan, the United Kingdom, Australia, and South America during the 19th and early 20th centuries. It chiefly prevailed in impoverished areas with poor hygiene and was often passed among family members. Until the 1950s, due to the absence of effective treatment, it posed a severe health crisis.
However, the situation improved with the introduction of griseofulvin, a drug used for treatment, in 1958. There were also enhancement of living conditions and anti-favus campaigns. These changes almost exterminated the disease caused by T. schoenleinii in the USA and Europe. Despite this, certain areas like Nigeria, Ethiopia, Western China, Iran, and some part of India still battle with the infection today, while it occurs infrequently in countries like Turkey, western Europe, and South America. In these areas, the disease may be mistaken for other conditions due to unusual presentations.
- Favus primarily affects children, primarily because they lack specific long fatty acids in their sebum that protect against fungi.
- Boys are at a higher risk of getting this disease as their short hair provides an easy pathway for spore circulation.
- Menopausal women are often affected by an adult version of the disease due to changes in their sebaceous glands resulting from decreased estrogen levels during menopause.
Signs and Symptoms of Favus
Favus, the most serious kind of tinea capitis or ringworm of the scalp, often goes unnoticed in its early stages, because it develops slowly and doesn’t have an acute phase. In most cases, it starts with red, scaly areas around hair follicles. When these areas are disrupted, a yellow crust known as a scutulum starts to form around a dull grey hair. The affected skin may have an unpleasant, cheesy odor, and will often glow bright green under a special type of light used by doctors known as Wood’s light. The condition can also lead to secondary bacterial infections that cause pus and swelling of the lymph nodes. Over time, as these yellow crusts merge and cover a third or more of the scalp, favus can lead to permanent hair loss and scarring.
Favus can also affect smooth, hairless skin and nails, although these cases are less common. On smooth skin, the condition can cause blister-like and scaly ring-shaped eruptions and typical yellow crusts. Skin thinning may occur in the affected areas. When it comes to nails, it’s hard to tell favus from other nail fungal infections. The fingernails can become infected when handling the scalp of another infected person. This used to be a common source of scalp reinfection after treatment, but nowadays it’s quite rare.
While widespread favus on the scalp and smooth skin was more common in the 1800s and early 1900s, these days it’s mostly seen in poor and rural areas. It’s extremely rare for favus to affect the entire body, but when it does, it can cause inflammation of mucus membranes, stomach upset, inflammation of the tube that connects your throat to your stomach (esophagus), and eye problems.
In a small percentage of cases, favus might not look like the typical yellow crusts and may have different features, such as scales that resemble dandruff or psoriasis, or pimple-like bumps. These atypical appearances might delay diagnosis and treatment.
Testing for Favus
: If your doctor suspects you might have a disease called favus, they might use a special type of light, called Wood’s light, on your skin. This light causes infected areas to glow dark green, which can help guide the doctor to the best place to take a sample.
After taking the sample, the doctor examines it under a microscope. The test works by mixing the sample with a solution containing 10% potassium hydroxide (KOH). The mixture will reveal the presence of fungus called endothrix infection. You picturing it as a a network of branching fungi (mycelium) and chains of tiny seed-like particles (spores) within the hair shafts.
A dead fungus can leave behind tiny air spaces which give us clues about the infection. Sometimes, the fungus needs to be grown in a laboratory for further testing. This process, known as a fungal culture, is one of the best ways to diagnose favus. The fungus, T. schoenleinii, is grown on a specific type of food for fungi, called Sabouraud glucose agar.
Over time, the fungus forms colonies that are slow-growing and have a unique appearance: they are waxy or downy with plenty of branching, have a brain-like (cerebriform) shape and a deep cream color at the top. The underside is tan-coloured. Once the fungus has grown, it is re-examined with the KOH test which reveals more specific features of the fungi that resemble shapes like a deer’s antlers, chandeliers, and nail heads.
A newer method of diagnosing favus is the polymerase chain reaction (PCR) test. This tool is extremely useful when normal fungal cultures fail. It works by detecting the DNA of the fungi, proving its presence in the sample. Using a PCR test, we can diagnose this rare fungal disease more accurately and efficiently.
Treatment Options for Favus
Favus, a type of fungal infection, was difficult to treat in the early years of the 19th-century and treatment relied on radiotherapy. Since 1958, the preferred method of treatment shifted to using an oral medication named griseofulvin, particularly when the favus is caused by a human-loving fungus called Trychophyton. However, the suggested doses and duration of the treatment have had to be increased because some strains of the fungus have evolved to resist griseofulvin. This is potentially because the fungus’ thick, multi-layered cell wall acts as a sort of shield against the medicine.
Unfortunately, griseofulvin has some major downsides, such as potential tendencies to cause cancer (carcinogenicity) and birth defects (teratogenicity). So, nowadays, doctors typically suggest using other antifungal medications, like terbinafine and azoles. These more modern medicines require shorter courses of treatment and have better risk-benefit ratios; plus, they stay present at levels that kill fungi in the body for several weeks after treatment has finished, which helps to prevent reinfection.
In addition to these systemic, or whole-body, treatments, local treatments (those applied to the site of the infection itself) can also play a helpful role. These may involve removing the scaly crusts that form over the infected areas, trimming the hair around any bald patches, and applying antifungal products (such as shampoos, foam gels, lotions, or sprays containing isoconazole and ketoconazole) to the site of the infection twice a day. Note that if the nails are involved, treatment may need to be continued for an extended period.
The success of these therapies can be confirmed by taking multiple fungal cultures from the patient over time and seeing negative (meaning ‘no growth of the fungus’) results.
What else can Favus be?
These are some conditions that can present with similar symptoms and may need to be ruled out when diagnosing certain skin disorders:
- Lichen planus
- Lupus erythematosus
- Amiantacea tinea
- Seborrhoeic dermatitis
- Psoriasis
- Kerion celsi
- Impetigo
- Sarcoidosis
- Folliculitis decalvans
- Squamous cell carcinoma, mainly in the cutaneous form
What to expect with Favus
Favus is a particularly severe form of a scalp infection known as tinea capitis. This long-lasting condition can cause significant damage, with substantial impacts on a person’s family life and social interactions.
Favus features a specific type of hair invasion called ‘endothrix infection’. This means that the infection is found inside the hair shaft, enabling the condition to persist as long as hair is present. Favus most often affects children and teenagers, and without treatment, it can continue into adulthood.
The success of treating favus depends largely on how early the condition is caught and treated. If diagnosed early and managed correctly, favus can be cured without any lingering effects. However, if treatment is delayed, the condition can lead to permanent hair loss in all cases, regardless of how it presents itself.
Possible Complications When Diagnosed with Favus
Common Issues:
- Permanent hair loss
- Physical alteration that may affect a person’s appearance
- Withdrawal from social activities
- Feeling of being judged or mistreated by others
- Various negative effects of the treatment
- Mental health challenges in children
Preventing Favus
There should be a thorough attempt to identify if a family member or someone from school is infected. Even if individuals do not show any signs of illness, they should be treated at the same time, because the disease can often go unnoticed. The disease, caused by T. schoenleinii, can leave behind spores for many years, which could lead to further spread of the disease.
Improving cleanliness routines with the scalp can be an essential step to reduce the presence of disease-causing germs. Also, it is important not to share personal items such as combs or hats to prevent the disease’s transmission.
All family members should be made aware of the significance of seeking medical help promptly and following medication guidelines properly. This education is crucial to prevent further transmission and ensure effective treatment.