Punctate keratolysis is a bacterial skin infection that can affect both the soles of the feet and the palms of the hands. However, it most commonly affects the feet due to the sweaty environment created by wearing shoes and socks for a long period of time.

This condition is characterized by small depressions or pits in the top layer of the skin and areas of white skin. It can be a cause of foot odor and is much more common in men than in women.

To better understand the process, we suggest reading the preamble by Dr. Eduardo Lauzurica

Punctate keratolysis, small holes under the sole of the foot and the microbiota.

It is fashionable to speak of “intestinal flora” and many of you know that there is also skin flora, as well as oral and vaginal flora. Some point out, why “flora” and not “fauna”, also to be in agreement with the terminology, it is more appropriate to say “microbiota”.

The fact is that the vastness of bacteria that live together in a healthy human body is becoming more and more important and we are becoming aware of the consequences of their imbalances.

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The term microbiota refers to the community of bacteria, fungi and viruses that we find in our body at any given time. They are commensal germs, not pathogens.

Some data allow us to imagine : the weight of microbiota in humans is estimated at 1 kg and the number of bacteria triples the number of carrier cells, with 300 times more DNA (microbiome, this time with “m”). (source)

At the local level, skin or mucous membranes, a correct status between microbiota and host makes it possible to inhibit inflammatory processes and this local regulation has systemic immunomodulatory effects.

The modification of these balances, dysbiosis, has local and general consequences. This dysbiosis seems to have an impact on situations as disparate as diabetes, obesity, the response to antineoplastic treatments, endogenous eczema and autoimmune processes.

Competition with pathogenic germs prevents the growth of pathogenic germs and therefore infections.

The microbiota in the skin reaches a coldness of 1 million bacteria per square centimeter and is less studied than that of the intestine. We found bacteria of the genus Corynebacteria, Propionybacteria, Staphylococcusmushrooms of the genus Malasseziaarthropods like Demodex foliculorum and some viruses.

The skin is therefore a good fertile ground and from these interactions is born the state of health of the individual or against dysregulatory situations and diseases.

All of this preamble because Punctate Keratolysis is a process that results from, say, dysbiosis of the sole of the foot.

In situations of increased humidity, either by hyperhidrosis or excessive occlusion, and increased pH, bacterial strains of the genus Corynebacterium proliferate in quantity and destroy keratin giving the plant skin capricious shapes.

The process was described more than a century ago as a variant of plantar hyperkeratosis (Castellani, 1910, “Keratoma plantare sulcatum”) and since 1965 it has been called “punctate keratolysis”, Zaias et al. to give it its new name, discovered the bacterial cause.

Corynebacteria (the pathogen that causes diphtheria also belongs to this group) are very abundant in the skin and are thought to be part of the microbiota. Some people under excessive colony growth would develop keratolysiswhich can coexist with two other processes such as erythrasma and trichomycosis, caused by the same germ.

What is observed in punctate keratolysis?

As the process tends to be asymptomatic, the occasional finding coincides with the exploration of another pathology or hyperhidrosis and/or bad foot odor.

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We observe small crevices, as if they had been made with a punch, which, when they converge, can reach surface erosions of 0.5 to several millimeters, confined in the stratum corneum (1-2 mm deep). They usually settle in the support (contact) areas of the sole of the foot and inflammation is usually absent. The hands are rarely affected.
Few people report discomfort or itching of the area.

The most common symptom of punctate keratolysis is noticeable foot odor.due to infection of the skin on the bottom of the feet.

People with this condition usually have clusters of ‘perforated’ pits on the soles of the feet or the palms of the hands. The pits will be more visible when the skin is wet. Sometimes these pits can unite to form larger lesions.

There is also a type of punctate keratolysis where the affected areas of the skin turn red. Although the pits themselves usually have no other symptoms, they are sometimes painful or itchy when pressure is put on the foot while walking.

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Why does punctate keratolysis occur?

The fault lies with the proteases that destroy keratin, separated by gender ” Corynebacterium ” and the ” Kytococcum sedentarius ” and ” Dermatophilus congolensis also involved.

Activities and professions that lead to lasting occlusion of the foot and therefore to increased humidity are the most predisposed: athletes, military and security forces, workers with protective footwear, farmers… Most cases are reported in adult males and described only in the elderly.

The accompanying foul odor is attributed to sulfur compounds resulting from the breakdown of keratin.

How to deal with punctate keratolysis?

The diagnosis is usually clinical and will rarely raise doubts with viral warts, arsenical keratoses, exfoliative keratolysis, tinea pedis or porokeratosis.

A biopsy would show localized loss of keratin and cocoid microorganisms ; in the deepest and most intense forms we will see dimorphisms with septal hyphae. The following link shows what it looks like with a electronic microscope (link)

The Wood lamp would in many cases delineate an area of ​​coral red fluorescence.

Read also : Burning soles of feet, what to do?

How to treat punctate keratolysis?

Treatment should be aimed at resolving the predisposing circumstances which, in the case of hyperhidrosis, involve the use of 20% aluminum hydrochloride. Bacterial elimination is effectively accomplished with topical antibiotics (lotion or cream twice a day) erythromycin, mupirocin, fusidic acid…, or with oral erythromycin for resistant cases.

To treat punctate keratolysis, your doctor will likely prescribe a topical antibiotic or antiseptic, most commonly clindamycin, erythromycin, or mupirocin. It is also recommended to avoid tight socks and shoes. In rare cases, your doctor may suggest a drying agent like Drysol.

In extreme cases, your doctor may recommend botulin injections to treat this condition.

In 2-3 weeks the skin aspect improves as well as the bad smell.

Can punctate keratolysis be treated with tea tree oil or cider vinegar?

Although tea tree oil and acetic acid (the active component of vinegar) have antibacterial properties in some settings, their use in the treatment of punctate keratolysis has not been evaluated in a clinical study. If you have punctate keratolysis, it is recommended that you treat your infection with a topical antibiotic prescribed by your doctor.

How to prevent punctate keratolysis?

As this bacterial infection thrives in moist environments, it is important to keep your feet as dry as possible to prevent punctate keratolysis. Take the following precautions to keep feet healthy and dry :

• Wear shoes for as little time as possible.
• Wear socks made of materials that absorb moisture, such as wool and nylon.
• Wear open-toed sandals as often as possible.
• Wash your feet frequently with an antiseptic cleanser.
• Avoid sharing your shoes with other people.