What is Dowling-Degos Disease?
Dowling-Degos disease (DDD) is a rare inherited condition. It is typically marked by an abnormal darkening of the skin in areas where the body bends, such as the knees or armpits. This usually starts after puberty, most frequently around the age of 30-40. It is thought to be caused by changes in certain genes that play a role in skin coloration and skin cell growth and communication. This darkening of the skin is often difficult to treat, as shown by the mixed results of treatments like creams and laser therapies.
What Causes Dowling-Degos Disease?
Classic DDD (Dowling-Degos Disease) and a version of it called Galli-Galli Disease are caused by a change in the structure of a protein-creating gene known as keratin 5 (KRT5). This change reduces the functioning capacity of the KRT5 gene.
There are also other genes that could play a part in these diseases. For instance, changes in the POFUT1, POGLUT1, and PSENEN genes, which are responsible for creating specific proteins, have been linked with DDD. Specifically, alterations in POFUT1 and POGLUT1 have been linked to a different form of DDD that usually affects non-flexing sites, while changes in the PSENEN gene have been associated with a version of DDD that is also connected with a skin condition called hidradenitis suppurativa.
Risk Factors and Frequency for Dowling-Degos Disease
DDD, first identified in 1938, is quite rare, with fewer than 50 known cases. It does not discriminate based on race or gender, typically showing up when people are in their 30s or 40s.
Signs and Symptoms of Dowling-Degos Disease
Dowling-Degos disease is a skin condition where patients notice dark patches typically appearing in the folds and creases of their bodies. This darkening of the skin can sometimes get itchy. The skin darkening starts out like freckle-like brown spots and small brown bumps and gradually intensifies over time. They first appear in the armpit and groin area, before showing up on the buttocks crease, below the breasts, neck, trunk, and inner arms and thighs.
Some patients may also have acne-like spots on their back and neck, pitted scars around their mouths, and rarely, small pits in their palms. There is a variant of this disease where patients develop painful, boil-like skin lumps (hidradenitis suppurativa) and round small lumps beneath the skin (epidermoid cysts). There have been few cases of patients with gene mutations having these dark patches in unusual areas of the body, not typically involved in this disease. Surprisingly, there has also been a report of a patient with Dowling-Degos disease having lighter (not darker) patches in the typically involved body areas.
Testing for Dowling-Degos Disease
DDD, also known as Dowling Degos Disease, is diagnosed using a combination of patient history, physical examination, and results from a skin biopsy. There’s no need for additional lab tests or imaging procedures for the diagnosis of this condition.
Treatment Options for Dowling-Degos Disease
Topical treatments like hydroquinone, tretinoin, adapalene, and corticosteroids have been used to treat hyperpigmentation, but these have had mixed results. Some success has been reported when using the Er:YAG laser followed by topical corticosteroids and fusidic acid. The idea behind the Er:YAG laser treatment is that it works by removing the overly grown skin, which then allows new, healthy skin to form from the unaffected skin cells.
What else can Dowling-Degos Disease be?
When diagnosing DDD, a skin condition that causes hyperpigmentation (darkening) in areas like armpits or the groin, doctors need to rule out other conditions that can cause similar symptoms. These include:
- Reticulate acropigmentation of Kitamura: This condition also causes dark skin patches, but it usually starts on the hands and feet and begins in childhood.
- Haber syndrome: This condition starts with a facial rash sensitive to sunlight during adolescence. It also leads to rough, pimple-like spots, small indented scars, and dark skin patterns on the chest, upper arms, and armpits. The facial rash tells doctors that Haber’s disease is different from DDD.
- Neurofibromatosis type 1: It has signs of dark freckling in armpit and groin areas, similar to DDD. But it gets easier to tell apart from DDD when small, benign skin tumors (neurofibromas) develop.
- Acanthosis nigricans: This condition has velvety, darkened skin patches that can be differentiated from DDD through a microscope examination. The skin structures called rete ridges are less elongated, and the hair follicles are not involved.
Therefore, detailed examination helps healthcare professionals to diagnose accurately.
