Dowling-Degos disease

Dowling-Degos disease is a skin condition characterized by a lacy or net-like (reticulate) pattern of abnormally dark skin coloring (hyperpigmentation), particularly in the body's folds and creases. These skin changes typically first appear in the armpits and groin area and can later spread to other skin folds such as the crook of the elbow and back of the knee. Less commonly, pigmentation changes can also occur on the wrist, back of the hand, face, scalp, scrotum (in males), and vulva (in females). These areas of hyperpigmentation do not darken with exposure to sunlight and cause no health problems.

Individuals with Dowling-Degos disease may also have dark lesions on the face and back that resemble blackheads, red bumps around the mouth that resemble acne, or depressed or pitted scars on the face similar to acne scars but with no history of acne. Cysts within the hair follicle (pilar cysts) may develop, most commonly on the scalp. Rarely, affected individuals have patches of skin that are unusually light in color (hypopigmented).

The pigmentation changes characteristic of Dowling-Degos disease typically begin in late childhood or in adolescence, although in some individuals, features of the condition do not appear until adulthood. New areas of hyperpigmentation tend to develop over time, and the other skin lesions tend to increase in number as well. While the skin changes caused by Dowling-Degos disease can be bothersome, they typically cause no health problems.

A condition called Galli-Galli disease has signs and symptoms similar to those of Dowling-Degos disease. In addition to pigmentation changes, individuals with Galli-Galli disease also have a breakdown of cells in the outer layer of skin (acantholysis). Acantholysis can cause skin irritation and itchiness. These conditions used to be considered two separate disorders, but Galli-Galli disease and Dowling-Degos disease are now regarded as the same condition.

Dowling-Degos disease appears to be a rare condition, although its prevalence is unknown.

Mutations in the KRT5 gene cause Dowling-Degos disease. The KRT5 gene provides instructions for making a protein called keratin 5. Keratins are a family of proteins that form the structural framework of certain cells, particularly cells that make up the skin, hair, and nails. Keratin 5 is produced in cells called keratinocytes found in the outer layer of the skin (the epidermis). Keratin 5 is one component of molecules called keratin intermediate filaments. These filaments assemble into strong networks that help attach keratinocytes together and anchor the epidermis to underlying layers of skin. Researchers believe that keratin 5 may also play a role in transporting melanosomes, which are cellular structures that produce a pigment called melanin. The transport of these structures into keratinocytes is important for normal skin coloration (pigmentation).

KRT5 gene mutations that cause Dowling-Degos disease lead to a decrease in the amount of functional keratin 5 protein that is produced. A reduction in keratin 5 can impair the formation of keratin intermediate filaments. As a result, the normal organization of the epidermis is altered, leading to the development of different types of skin lesions. Additionally, a decrease in keratin 5 may disrupt the movement of pigment-carrying melanosomes into keratinocytes, where they are needed for normal skin pigmentation. This disruption of melanosome transport is thought to cause the pigmentation abnormalities seen in individuals with Dowling-Degos disease.

Some people with Dowling-Degos disease do not have an identified mutation in the KRT5 gene. In these cases, the cause of the condition is unknown.

Related Gene(s)

Changes in this gene are associated with Dowling-Degos disease.

• KRT5

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In most cases, an affected person has one parent with the condition.