What is tinea manuum?
Tinea manuum is a fungal infection of the hand caused by dermatophytes, a type of fungi. The infection is superficial and limited to the outer layers of the skin as is typical of dermatophyte infections. It is uncommon compared to other fungal infections of the extremities – tinea pedis (feet) and tinea unguium (nails). Dermatophyte infection is commonly referred to as a ringworm due to the characteristic round to oval rash which may not be as clearly evident with tinea manuum. Nevertheless, the infection is largely similar to other forms of dermatophytosis such as tinea corporis (body ringworm) and tinea pedis (athlete’s foot).
How does hand fungus occur?
The outer layers of the skin are composed of dead skin cells laden with a protein known as keratin. This makes the outer skin tough and waterproof protecting the delicate inner environment of the body. Healthy skin is able to withstand most microbes and rapidly heals when injured. However, when the skin is unhealthy and should a break in the skin occur with slow healing, various types of infections can set in. There is an even greater risk when the body’s defenses are unable to quickly fight off the infection.
Dermatophytes are a types of fungi that tend to cause superficial infections of the outermost layers of the skin. It has specialized enzymes known as keratinases which can digest the skin protein and allows the fungus to establish itself on the skin. Here it grows further over time. These fungi can be passed on from person to person (anthropophilic), from animals to humans (zoophilic) or from the soil to humans (geophilic). One of the most common ways that a hand fungus arises is with contact with a dermatophyte infection elsewhere on the body like the feet or groin. Constant scratching of the ringworm rash on these areas transfers the fungus to the hand.
Causes of Tinea Manuum
There are various different species of dermatophytes that can cause a fungal infection of the hand. The most common have a predilection for humans (anthropophilic fungi) and includes :
- Trichophyton rubrum (T.rubrum) which is the most common cause of skin fungal infections in humans.
- Trichophyton interdigitale
- Epidermophyton floccosum
Other species of fungi may be transmitted to the hands through contact with animals (zoophilic) or inanimate objects contaminated with soil (geophilic) :
- Microsporum canis – from dogs or cats
- Trichophyton verrucosum – from cattle
- Microsporum gypseum – from soil
Another type of fungus that affects the hands is a geophilic mold which causes tinea nigra. This type of fungal infection can also affect the soles and causes a brown to black patches on the palms and soles. Tinea nigra is caused by different species of fungi than those mentioned above and due to the difference in presentation, it is usually not confused with tinea manuum.
Although a hand fungus can occur in any person, it is more likely to arise in the following scenarios :
- Pre-existing dermatophyte infection elsewhere on the body.
- Close personal contact with a skin fungal infection.
- Person who sweats excessively (hyperhidrosis) or has other skin diseases.
- Regular contact with pets which is a more likely cause in children.
- Farm workers handling livestock, particularly cattle, or soil.
- Gardeners due to regular contact with soil and other manual laborers through inanimate objects (fomites) contaminated with soil.
Signs and Symptoms
Tinea manuum presents with an itchy rash on the hand which may involve the fingers as well. Nail fungus is referred to as tinea unguium. The characteristics of the rash are as follows :
- Dry peeling skin more frequently seen with anthropophilic fungi.
- Red raised borders with healing the middle of the rash creating a ring-like appearance which is seen more commonly with zoophilic or geophilic fungi.
- Crops of tiny blisters especially on the sides of the fingers and palm which may be oozing.
- Itching and burning which may vary in intensity.
- Discoloration of the skin which typically develops if the rash heals after existing for very long periods. This should not be confused with tinea nigra which causes dark brown to black patches on the palms.
Tinea manuum can present similar to many other skin conditions that affect the hands including allergic and irritant contact dermatitis, psoriasis and dyshidrotic dermatitis (pompholyx). In some cases, the fungal infection may set in secondary to these conditions as the diseased skin leaves it prone to infections. Therefore the presentation may not be typical.
|Picture of tinea manuum on the back of the hand. Note the typical ringworm appearance.||Picture of tinea manuum on the palms and also involving the fingers.|
|Pictures sourced from Dermatology Atlas Brazil (2) courtesy of Samuel Freire da Silva, M.D.|
|Picture of tinea manuum (hand fungus) on the palms extending up towards the fingertips.|
Diagnosis of Tinea Manuum
The diagnosis is made by the clinical presentation and other skin diseases that have a similar appearance should be excluded. Further diagnostic investigations are the same as for other dermatophyte infections and may involve skin scrapings, fungal cultures or biopsy. A characteristic clinical sign that is indicative of the skin rash being fungal in origin is known as the “two feet – one hand” syndrome. In this instance both feet may have the same dermatophyte rash (tinea pedis) and one hand (tinea manuum). It is typically the dominant hand or hand that is used for scratching the feet that is affected with the rash.
Treatment of Tinea Manuum
Antifungal medication can completely eradicate the fungi within 4 to 6 weeks and is curative. It may involve the use of both oral and topical antifungals.
- Topical antifungals (ointments and gels) – terbinafine, clotrimazole, ciclopirox, econazole or butenafine.
- Oral antifungals (tablets and capsules) – terbinafine, fluconazole, itraconazole or griseofulvin.
Underlying predisposing conditions such as hand dermatitis and palmar hyperhidrosis (sweaty palms) should also be treated and effectively managed. The hand being the most active appendage is in constant contact with people, animals and contaminated objects that makes it easy to contract various infections. Without treating the underlying condition the hand fungus may recur.
1. Tinea manuum. DermNet NZ
2. Tinea manuum pictures. Dermatology Atlas Brazil
3. Ringworm (tinea). Merck Manuals