Pitted keratolysis is a superficial bacterial skin infection that affects the soles of the feet because of the sweaty environment created by wearing shoes and socks for an extended period of time, and less often, the palms of the hands. It is one of the causes of smelly feet and characterized by whitish skin and clusters of punched-out pits, which is much more common in men than women. The bacterial skin infection is caused by several bacterial species, including Corynebacteria, Dermotophilus congolensis, Kytococcus sedentorius, Actinomyces, and Streptomyces. This condition is characterized by small depressions or pits in the top layer of skin and areas of white skin.

The bacteria proliferate in moist conditions (These bacteria often multiply in wet or moist conditions). This is why people who don’t let their feet air out enough often develop it. The pitting is due to the destruction of the horny cells (stratum corneum) by protease enzymes produced by the bacteria. The bad smell is due to sulfur compounds produced by the bacteria: thiols, sulfides, and thioesters.

Occupations having people at risk include farmers, athletes, sailors or fishermen, industrial workers, military personnel, females offering pedicure and foot care in a spa salon may also be affected by pitted keratolysis.

Factors that lead to the development of pitted keratolysis include hot, humid weather, Occlusive footwear (such as rubber boots or vinyl shoes), excessive sweating of hands and feet (hyperhidrosis), the thickened skin of palms and soles (keratoderma), Diabetes mellitus, advanced age, immunodeficiency.

The most common symptom of pitted keratolysis is a noticeable odor from the feet due to the infection of the skin on the bottom of the feet. Those with this condition will usually have clusters of “punched-out” pits on the soles of their feet or palms of their hands. The pits will be more noticeable when the skin is wet. Sometimes these pits can join together, or “coalesce,” to form larger lesions.

There’s also a type of pitted keratolysis where the affected areas of the skin turn red. While the pits themselves usually won’t present with other symptoms, they sometimes feel sore or itch when pressure is put on the foot while walking.

If you think you have pitted keratolysis, see a doctor. Pitted keratolysis is usually diagnosed clinically. you will need antibiotics to treat the infection. To diagnose, you with pitted keratolysis, your doctor will swab the area or do something called a skin scraping, where your doctor obtains a sample of skin to check for bacteria and parasites under a microscope. The causative organisms may be identified from the pitted lesions and cultured on brain heart infusion agar. Skin scrapings are often taken to exclude fungal infection. Wood light examination displays a characteristic coral red fluorescence in some cases. The diagnosis is sometimes made by skin biopsy revealing characteristic histopathological features of pitted keratolysis.

To treat pitted keratolysis, your doctor will most likely prescribe a topical antibiotic and antiseptic, most commonly clindamycin, erythromycin, mupirocin, fusidic acid, and Benzoyl peroxide. Oral erythromycin is also helpful. It’s also recommended that you avoid tight-fitting socks and shoes. ln rare cases, your doctor may suggest a drying agent like Drysol in extreme cases, your doctor may recommend shots of botulin to treat this condition.

Pitted keratolysis will quickly recur unless the feet are kept dry. The following precautions should be taken to prevent recurrences:

  • Wear boots for as short a period as possible.
  • Wear socks which effectively absorb sweat, ie cotton and/or wool.
  • Wear open-toed sandals whenever possible
  • Wash feet with soap or antiseptic cleanser twice daily
  • Apply antiperspirant to the feet at least twice weekly
  • Do not wear the same shoes two days in a row – dry them out.
  • Do not share footwear or towels with others.

SOLES OF FEET

pitted keratolysis

The sole is the underside of the foot. ln humans, the sole of the foot is anatomically referred to as the plantar aspect. The glabrous skin on the sole of the foot lacks the hair and pigmentation found elsewhere on the body, and it has a high concentration of sweat pores. The sole contains the thickest layers of skin on the body due to the weight that is continually placed on it. It is crossed by a set of creases that form during the early stages of embryonic development of the palm, the sweat pores of the sole lack sebaceous glands.

The sole is a sensory organ by which we can perceive the ground while standing and walking. The subcutaneous tissue in the sole has adapted to deal with the high local compressive forces on the heel and the ball (between the toes and the arch) by developing a system of “pressure chambers.” Each chamber is composed of internal fibrofatty tissue covered by external collagen connective tissue. The septa (internal walls) of these chambers are permeated by numerous blood vessels, making the sole one of the most vascularized, or blood-enriched, regions in the human body.

The sole and the longitudinal arch of the foot are supported by a thick connective tissue and the plantar fascia. The central component of this tissue extends to the supporting bones and gives two divisions-the medial component and lateral component thus they define the boundaries of the three muscle compartments of the sole (see below).

The bones underlying the sole form the arch of the foot. The arches might collapse later in life, resulting in flat feet.

TYPES OF FOOT FUNGUS

Fungal infections of the skin on the feet are common. Most are due to one type of fungal infection but other less common and even rare fungi can also cause infections of the feet. For example, thrush is caused by Candida albicans, a type of yeast, and this fungus can also infect the skin on the feet. However, “thrush of the foot” is rare. There are several reasons why fungal infections are more likely to occur on the feet. Understanding why this may occur on the feet, in particular, can help to prevent future infections after treatment.

Although fungi are in one kingdom of organisms, there are many different families and species of fungi. Most fungal infections of the human skin, whether on the foot or elsewhere on the body, are caused by dermatophytes. Less commonly, yeasts can also infect human skin.

Candida species

The Candida species of yeasts are the main cause of these type of skin infections but another rare yeast can also cause an infection of the skin on the feet, particularly on the soles.

Dermatophytosis

This refers to skin infections caused by dermatophytes. It also includes dermatophyte infections of hair and nails. Dermatophytes are one type of fungi that have a predilection for human skin. These fungi contain enzymes which can digest keratin, the protein that forms the outer layers of the skin. Dermatophytes are the most common type of fungi to cause fungal skin infections.

Candidiasis: Yeast infections of the skin are far less common although this type of fungi causes infections of the vagina and mouth which are referred to as vaginal thrush and oral thrush, respectively. The main yeast to infect humans is Candida albicans. Skin infections by this species of yeasts are known as cutaneous candidiasis. It is more likely to occur when the skin is broken and particularly at folds of skin, like between the toes of the feet. Tinea Nigra: Tinea nigra is a type of fungal skin infection that mainly affects the palms of the hand and soles of the feet. It is a rare fungal infection mainly caused by a specific species of yeast. This is not the Candida species of yeast as is therefore not discussed under cutaneous candidiasis. A characteristic feature of tinea nigra infection is that it causes a dark brown to black spot or patch atthe site of the infection.

Athlete’s Foot

pitted keratolysis

The most common fungal infection of the foot, known as tinea pedis or athlete’s foot, is usually caused by the dermatophyte Trichophyton rubrum. Other fungi such as Trichophyton interdigitale and Epidermophyton floccosum are also responsible for athlete’s foot. It may occur anywhere on the skin of the feet. The risk of contracting this infection is greater in regions that are hot and humid. Sharing personal items like towels and footwear as well as using common facilities like showers also increase the risk of athlete’s foot spreading from one person to another. Certain fungal species in the soil and on animals can be spread to humans.

Foot Candida (Thrush)

Candida Albicans the most common yeast to cause fungal infections of the skin on the feet. This species of fungi is widespread in the environment as well as in cavities such as the mouth. It may naturally occur on the skin folds in some people but this may not always cause an infection at the site.

Fungi are found throughout the globe and are widely prevalent in the environment. It is found in the air, on surfaces, on humans and other animals, as well as in the soil. Some fungal species are more common than others and yeasts like Candida may naturally occur on the human skin. Although people come into contact with fungi on a constant basis, this does not usually lead to an infection. The skin is a physical barrier that can prevent a fungal infection from arising if it is healthy. Similarly, the cavities like the mouth are able to prevent an infection if there is the correct balance of other microorganisms present within it. The immune system will also keep fungi from causing an infection. However, these mechanisms are not always functioning properly or sufficient to prevent an infection from fungi in every instance.

Furthermore, fungi need certain environmental conditions to thrive. It prefers moist areas, such as the feet and groin. Warmth is another factor that helps fungal growth. A break in the skin increases the risk of a fungal infection. Some people may have a genetic susceptibility to fungal skin infections. There is also a greater risk if their close skin-to-skin contact with a person who has an infection. Even sharing items and facilities can spread the fungi.