‘Keratoderma’ is a term that means marked thickening of the epidermis of the skin.
‘Palmoplantar’ refers to the skin on the soles of the feet and palms of the hands; these are the areas keratoderma affects most often. Palmoplantar keratoderma is also sometimes known as ‘keratosis palmaris et plantaris’.
Classification of keratodermas depends on whether it is inherited or acquired, and the clinical features.
Most often the abnormal skin involves only the palms and soles (non-transgradient palmoplantar keratoderma) but sometimes it extends on to the top of the hands and feet as well (transgradient).
In some rare syndromic forms of keratoderma other organs in the body may be affected in addition to the skin, and the keratoderma can be a marker of this internal abnormality.
Diffuse palmoplantar keratoderma
Focal palmoplantar keratoderma
Punctate keratoderma
What causes palmoplantar keratoderma?
Keratoderma may be inherited (hereditary) or, more commonly, acquired.
Hereditary keratoderma: the condition runs in families and is passed down or from one or both parent(s) to their children
Acquired keratoderma: the condition is not inherited and occurs as a result of a change in the health or the environment of the affected person
The hereditary keratodermas are caused by a gene abnormality that results in abnormal skin protein (keratin). They may be inherited either by an autosomal dominant or autosomal recessive pattern.
Autosomal dominant keratodermas are likely to occur in every generation of a family. If one parent is affected there is a 50% chance that each child will be affected.
Autosomal recessive keratodermas occur less commonly within an affected family. This is because both parents need to pass on an abnormal gene to the child for it to be affected. People with one affected gene only do not have the condition themselves but carry the abnormal gene and are referred to as ‘carriers’ of the disease. They may pass on the abnormal gene to their children but the children will only be affected if their other parent also carries an abnormal gene and passes it on to the same child.
A specific gene mutation may be found within 13 different genes.
Specific types of keratoderma
The table below lists the main types of hereditary palmoplantar keratoderma (PPK).
