Palmoplantar keratoderma (PPK) is a group of skin conditions characterized by thickening of the skin on the palms of the hands and soles of the feet. PPK can also be a feature of various underlying syndromes. In rare forms of PPK, organs other than the skin may also be affected. PPK can be either acquired during the lifetime (more commonly) or inherited. Acquired PPKs may arise due to changes in a person's health or environment. Inherited PPKs are caused by genetic mutations that result in abnormalities of keratin, a skin protein. Depending on the genetic cause, inheritance can be autosomal dominant or autosomal recessive. Treatment is aimed at softening the thickened skin to make it less noticeable and relieve discomfort.

Inherited forms of PPK are caused by genetic mutations that result in abnormalities of keratin (a skin protein). These forms of PPK may be present in more than one family member. Mutations in several genes can cause an inherited form of PPK. Depending on the gene involved, inheritance can be autosomal dominant or autosomal recessive.

Autosomal dominant inheritance means that having a mutation in only one copy of the responsible gene in each cell is enough to cause features of the condition. In some cases, an affected person inherits the mutated gene from an affected parent. In other cases, the mutation occurs for the first time in a person with no family history of the condition. This is called a de novo mutation. When a person with a mutation that causes an autosomal dominant condition has children, each child has a 50% (1 in 2) chance to inherit that mutation. For this reason, it is not uncommon for an autosomal dominant condition to be present in more than one generation in a family.

Autosomal recessive inheritance means that to be affected, a person must have a mutation in both copies of the responsible gene in each cell. Affected people inherit one mutated copy of the gene from each parent, who is referred to as a carrier. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When 2 carriers of an autosomal recessive condition have children, each child has a:

• 25% chance to be affected
• 50% chance to be an unaffected carrier like each parent
• 25% chance to be unaffected and not a carrier

A person with an autosomal recessive condition can have an affected child only if the child's other parent is at least a carrier of the same condition. In most cases, autosomal recessive conditions affect only one generation in a family, such as siblings.

People with personal questions regarding whether PPK is inherited, or how it may be inherited, are encouraged to speak with a genetic counselor or other genetics professional. A genetics professional can help by:

• thoroughly evaluating the family history
• addressing questions and concerns
• assessing recurrence risks
• facilitating genetic testing if desired
• discussing reproductive options

In addition to identifying thickened skin on the palms of the hands and soles of the feet, an exam is needed to check for involvement of other areas of the skin; the nails, hair, and teeth; and other organs of the body. Distinguishing between acquired and hereditary PPK is important. Acquired PPK usually occurs later in life and may be due to many causes, such as drugs, malnutrition, chemicals, systemic disease, cancer, and infection.

The family history may be helpful in identifying hereditary PPK and establishing the inheritance pattern. Lack of a family history is not necessarily evidence of acquired PPK. Autosomal recessive PPK can appear sporadically from unaffected parent carriers, and autosomal dominant PPK can also occur sporadically due to a new mutation in an affected person (a de novo mutation).

Histopathology of a biopsy from affected skin should be part of the diagnostic workup. This may show more specific features characteristic of a subtype of PPK. Distinguishing between epidermolytic and nonepidermolytic forms of PPK is helpful for treatment options, as epidermolytic forms tend to worsen on systemic retinoids. Histopathology is also needed to rule out other conditions with overlapping features.

Genetic testing allows for a precise diagnosis as well as counseling with regard to the inheritance pattern and risk of recurrence. The Genetic Testing Registry (GTR) provides information about the genetic tests for each hereditary type of PPK. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Treatment options may depend on the specific type of PPK a person has and may include:

• Saltwater soaks
• Emollients
• Paring (cutting away layers of skin)
• Topical keratolytics (useful for people with limited keratoderma)
• Topical retinoids (this is often limited by skin irritation)
• Systemic retinoids (acitretin)
• Topical vitamin D ointment (calcipotriol)
• Surgery to remove the skin, followed by skin grafting
• Potent topical steroids with or without keratolytics in cases with an inflammatory component
• Psoralens and ultraviolet A (PUVA) or re-PUVA (a combination of oral retinoids and PUVA) in some people with PPK secondary to psoriasis or eczema

Currently, to our knowledge, there is no way to prevent PPK in a person who has inherited PPK but has not yet developed symptoms.