Dowling-Degos disease

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

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, back of the knee, and under the breasts. Less commonly, pigmentation changes can also occur on the neck, wrists, back of the hands, face, scalp, scrotum, and vulva. These areas of hyperpigmentation typically cause no health problems.

Individuals with Dowling-Degos disease may also have dark spots (lesions) on the face and back that resemble blackheads, red bumps around the mouth that resemble acne, or pitted scars on the face similar to acne scars but with no history of acne. Fluid-filled sacs 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).

In rare cases, individuals with Dowling-Degos disease experience itching (pruritus) or burning sensations on the skin. These feelings can be triggered by UV light, sweating, or friction on the skin.

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 associated with Dowling-Degos disease may cause distress or anxiety, they typically cause no other 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 and lead to reddened or missing patches of skin (erosions). These conditions used to be considered two separate disorders, but Galli-Galli disease and Dowling-Degos disease are now regarded as the same condition.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the KRT5, POFUT1, or POGLUT1 gene cause most cases of Dowling-Degos disease.

The KRT5 gene provides instructions for making a protein called keratin 5, which is produced in cells called keratinocytes 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 (bind) 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 pigment-carrying structures found in skin cells called melanocytes. The transport of these structures from melanocytes into keratinocytes is important for the development of normal skin coloration (pigmentation).

The POFUT1 and POGLUT1 genes provide instructions for making proteins that add different sugar molecules to proteins called Notch receptors. Notch receptors are a family of proteins that are involved in a signaling pathway that guides normal development of many tissues throughout the body, both before birth and throughout life. Receptor proteins have specific sites into which certain other proteins, called ligands, fit like keys into locks. The addition of sugar molecules to Notch receptors changes the shape of the receptors, allowing them to bind to their ligands and trigger signaling in the pathway. In skin cells, Notch signaling likely plays a role in maintaining precursor cells that mature into melanocytes and regulating interactions between melanocytes and keratinocytes.

KRT5 gene mutations that cause Dowling-Degos disease lead to a decrease in functional keratin 5 protein. A loss of 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 transfer of pigment-carrying melanosomes from melanocytes to keratinocytes, where they are needed for the development of normal skin pigmentation. This disruption of melanosome transport is thought to cause the pigmentation abnormalities seen in individuals with Dowling-Degos disease.

Mutations in the POFUT1 or POGLUT1 gene result in a protein with little or no function. As a result, the protein is less able or unable to add sugar molecules to Notch receptors. Without these sugar molecules, Notch receptors cannot bind to their ligands and the Notch signaling pathway is halted. Because the varied functions of the Notch signaling pathway affect many body systems and Dowling-Degos disease affects only the skin, it is unclear whether the signs and symptoms of this condition are due to impaired Notch signaling or disruption of an unknown function of the protein in melanocytes or other skin cells.

Mutations in other genes, some of which have not been identified, are responsible for the remaining cases of Dowling-Degos disease.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

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.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

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

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Progressive reticulate hyperpigmentation · Very frequent (99-80%)

Abnormality of the neck · Frequent (79-30%)

An abnormality of the neck.

Hyperkeratosis · Frequent (79-30%)

Hyperkeratosis is a histopathological term defining a thickened stratum corneum and may be present in many different skin conditions, with many possible overlaps. Hyperkeratosis refers to the increased thickness of the stratum corneum, the outer layer of the skin. Hyperkeratosis is subclassified as orthokeratotic or parakeratotic. Orthokeratotic hyperkeratosis refers to the thickening of the keratin layer with preserved keratinocyte maturation, while parakeratotic hyperkeratosis shows retained nuclei as a sign of delayed maturation of keratinocytes.

Inguinal freckling · Frequent (79-30%)

The presence in the inguinal region (groin) of an increased number of freckles, small circular spots on the skin that are darker than the surrounding skin because of deposits of melanin.

Abnormal fingernail morphology · Occasional (29-5%)

An abnormality of the fingernails.

Abnormality of the hand · Occasional (29-5%)

An abnormality affecting one or both hands.

Acne inversa · Occasional (29-5%)

A chronic skin condition involving the inflammation of the apocrine sweat glands, forming pimple-like bumps known as abscesses.

Digital pitting scar · Occasional (29-5%)

Pinhole-sized concave depressions with hyperkeratosis in the skin of a finger or toe.

Other findings in the same source

From: Orphanet

Additional reported features include Erythematous papule (Occasional (29-5%)); Heat intolerance (Occasional (29-5%)); Hyperkeratotic papule (Occasional (29-5%)); Hypermelanotic macule (Occasional (29-5%)); Hyperpigmented papule (Occasional (29-5%)); Penile freckling (Occasional (29-5%)); Pruritus (Occasional (29-5%)); Scrotal hyperpigmentation (Occasional (29-5%)); Anal margin squamous cell carcinoma (Very rare (<4-1%)); Arthritis (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Dowling-Degos disease is Dermatology, with a dermatologist as the relevant type of clinician. Dermatologist; paediatric services for children as appropriate.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which features of the skin, hair or nails distinguish the possibilities?
• Would photographs over time help document the changes?
• What should be expected from treatment, and how will irritation or other adverse effects be managed?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Dowling-Degos disease. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.