The term hereditary palmoplantar keratosis is used to describe a variety of different, genetically determined keratinization disorders of the palms and soles of the feet. These are diffuse or focal palmoplantar hyperkeratoses. The inherited forms of palmoplantar keratoses are predominantly inherited in an autosomal dominant manner and usually appear in early childhood during the first or second year of life.
What is hereditary palmoplantar keratosis?
The variety of manifestations of genetically determined hyperkeratosis of the palms and the soles of the feet summarized under the term hereditary palmoplantar keratosis (PKK) presents with an equally large variety of symptomatology. Acquired palmoplantar hyperkeratoses also present themselves with an equally great variety. They are caused by infections, pollutants or as a side effect of medications. An important, but not sufficient, distinguishing feature between the two forms is the time of onset of the disorder. In most genetic forms of hyperkeratosis, the first symptoms appear in early childhood at one or two years of age. Acquired forms of the disease do not appear until after contact with the causative substance, usually in adulthood. Frequently, hereditary palmoplantar keratoses are associated with functional impairment of other organs such as eyes or ears, or with developmental disorders of the central nervous system. Some hereditary palmoplantar keratoses are not directly but indirectly caused by a genetic enzyme defect like Richner-Hanhart syndrome. The syndrome is identical to tyrosinemia type II. Because of a gene mutation, extraordinary accumulation of the amino acids tyrosine and phenylalanine occurs, causing, among other things, the disease symptoms of palmoplantar hyperkeratosis.
Causes
The variety of manifestations of hereditary palmoplantar keratoses already suggests that it cannot be a single genetic defect that causes the disease. In fact, causative mutations have been documented on many different genes that may be located on different chromosomes. These are usually genes that encode specific keratin proteins. Gene mutations result in miscoding of the proteins, which is usually associated with loss of function. In a few cases, such as Richner-Hanhart syndrome, a gene mutation does not lead to a miscoding of a keratin protein but, for example, to a blockade of tyrosine aminotransferase, so that tyrosine and phenylalanine can accumulate extremely in the body. The resulting palmoplantar keratosis thus also fulfills characteristics of acquired hyperkeratosis.
Symptoms, complaints, and signs
In the uppermost layer of the human skin, the epidermis or cuticle, fresh skin cells form in a continuous process in the basement membrane that separates the epidermis from the dermis or dermis. These are horny cells that gradually migrate to the surface of the skin, losing their nucleus and becoming increasingly keratinized within the epidermis. The migration of the cells from the basement membrane to the surface of the skin takes 28 days. Once there, the horny platelets are exfoliated in tiny, barely visible flakes of skin. In the presence of hereditary palmoplantar keratosis, the transformation process of a keratin-containing skin cell to a dead horny platelet is disturbed. It may also occur that the reproduction rate of skin cells in the basement membrane of the epidermis is greatly increased (hyperkeratosis). Most manifestations of hereditary palmoplantar keratosis can already be recognized by specific and typical features of the affected skin areas. The first symptoms usually appear in the form of skin lesions and excessively thick corneas.
Diagnosis and course
Indirect indications of the presence of hereditary PKK, i.e., hereditary PKK, are early onset at one to two years of age and associated dysfunction of other organs or organ systems, such as hearing currents or visual disturbances, neurologic abnormalities, hyperhidrosis, and persistent resistance to therapy. A carefully conducted family history, revealing other cases of palmoplantar keratosis in family members, corroborates the diagnosis that it is an inherited form of the disease.Certain courses also include hair and nails, and as the disease progresses, the affected areas of skin may extend beyond the soles of the feet and palms of the hands. The palms of the hands and soles of the feet may show different manifestations of genetic PKK. For example, the soles of the feet may be affected by diffuse areas, whereas the palms may show accentuated, striated, or punctate keratinization disorders.
Complications
In this disease, there are changes and skin complaints that occur mainly on the feet. This results in a thick callus. In some cases, this can lead to walking difficulties or pain, significantly reducing the patient’s quality of life. In most cases, palmoplantar keratosis also causes discomfort in the ears and eyes, and in the worst case, the affected person may go completely blind or lose all hearing. Likewise, neurological complaints occur, which in some cases can also lead to paralysis and other disturbances of sensitivity. It is not uncommon for the symptoms to spread to the hair and nails. In these cases, patients also suffer from decreased self-esteem and inferiority complexes due to the aesthetic changes. The treatment is mainly aimed at alleviating the symptoms and thus does not lead to further complications. As a rule, the disease can be well limited by a change in diet, so that the complaints disappear completely. In some cases, surgical interventions are necessary. Life expectancy is not limited or reduced by palmoplantar keratosis.
When should you see a doctor?
Since this disease does not heal itself and usually worsens the symptoms, treatment must always be provided by a doctor. A doctor should be consulted if the patient suffers from keratinization disorder. This can occur already in childhood and affect different regions of the skin. As a rule, it results in a highly keratinized and scaly skin. If these complaints occur without a particular reason and above all permanently, a doctor must be consulted without fail. The dermatologist and general practitioner are initially the right contacts. Since the skin complaints can often also lead to psychological complaints, psychological treatment is also advisable. Frequently, disorders of the internal organs or the eyes also indicate the disease and should be examined. Either the ophthalmologist or the internist can determine these disorders.
Treatment and therapy
Currently, no therapy exists to cure inherited PKK, so all forms of treatment are limited to symptom relief and prevention of infection. Exceptions are those forms of the disease that are only indirectly caused by one or more mutated genes, such as the above-mentioned Richner-Hanhart syndrome, in the course of which PKK develops quasi as a concomitant symptom. The keratosis regresses if the affected person changes his diet to components that are as low in tyrosine as possible, without the disease being considered cured as a result. Depending on the manifestation of the disease, treatment consists of mechanical removal of excess horny structures or even surgery. Some variants of inherited PKK respond to acitretin. As a derivative of vitamin A, this slows down the formation of corneal cells and is used primarily to treat psoriasis. The drug is not without side effects. Side effects such as nosebleeds, visual disturbances and skin dryness are frequently reported, and prolonged use leads to an increase in cholesterol levels.
Outlook and prognosis
The prognosis of hereditary palmoplantar keratosis depends on the specific disease. It is a group of genetically determined cornification disorders of the skin on the hands and feet. The diseases are all congenital. Usually, the first symptoms begin in early childhood. Due to their genetic cause, these skin diseases cannot be cured. Only symptomatic therapies are possible, which can bring some relief to the affected patients. The group of hereditary palmoplantar keratoses includes both diffuse and focal palmoplantar hyperkeratoses.In focal palmoplantar hyperkeratoses, the cornification processes are demarcated, whereas in diffuse palmoplantar hyperkeratoses, larger areas are affected. In most cases, life expectancy is normal. However, there are also diseases with decreased life expectancy such as keratoderma with esophageal carcinoma, among others. Epidermolytic palmoplantar keratosis represents the most common form of hereditary palmoplantar keratoses. It is characterized by diffuse but sharply demarcated keratinization disorders on the extensor sides of the hands and feet with clock glass nails. Some diseases still show involvement of the ears with the formation of sensorineural hearing loss in addition to extensive hyperkeratosis. Examples are the diseases keratoderma hereditarium mutilans or KID syndrome. Although life expectancy is usually not limited, the affected patient often suffers from a greatly reduced quality of life. This, in turn, depends on success of cosmetic treatment with keratolytics, which help to dissolve and ablate the excessively formed cornea.
Prevention
Preventive measures to prevent genetic palmoplantar keratosis do not exist. If cases of the disease have been reported within the family, newborns are at increased risk of developing one of the many possible variants of PKK. Molecular genetic testing is only useful if it is known which gene might be affected. Otherwise, a genetic test could come back negative without any assurance that PKK cannot occur.
Follow-up
In most cases, the affected person has no or only very few direct measures and possibilities of aftercare available for this palmoplantar keratosis. In this regard, the affected person should contact a physician at the first signs and symptoms of the disease so that the symptoms do not continue to worsen. In general, early detection of the symptoms has a very positive effect on the further course of the disease and can also prevent further complications. In most cases, the symptoms of palmoplantar keratosis can be alleviated and completely limited by a proper diet, so that it is not necessary to take medication. In this case, the doctor can also prepare a diet plan for the parents, according to which the child should be fed. The dry skin should be treated with creams and ointments in this disease, so that there are no cracks or other discomforts on the skin. In most cases these complaints disappear after the treatment, so that no special measures of an aftercare are necessary any more. Since palmoplantar keratosis is a hereditary disease, it cannot be completely cured. Therefore, if the patient wishes to have children, genetic testing and counseling may also be useful to prevent the recurrence of the disease.
What you can do yourself
Hereditary palmoplantar keratosis cannot yet be treated causally. The symptoms can be reduced by the affected person taking dietary measures. A diet as low in tyrosine as possible and avoidance of coffee, alcohol and cigarettes are recommended. Patients should also eat a balanced diet rich in vitamins. Sports and sufficient sleep support the healing of the horn structures and increase well-being, which is often reduced, especially in chronic diseases. Lastly, sparing and strict personal hygiene apply to hereditary palmoplantar keratosis. The horn structures can sometimes be reduced with pumice stones and similar aids. In order to prevent the formation of painful cornifications in the first place, the development of pressure points should be avoided. Appropriate footwear and suitable clothing significantly reduce the risk of complicated horn structures. Women suffering from the disease should have a genetic examination of the child after childbirth. Through early diagnosis, the hereditary disease can be treated well and, in the best case, does not form any symptoms. A genetic test is also recommended if the child’s father or another family member suffers from PKK.
