Dowling-degos disease is a rare condition of the skin that presents dark skin coloring (hyperpigmentation) particularly in the folds of the skin. This genetic disease is also known as pigmented reticulate anomaly of the flexures. It usually develops in the adults, particularly among individuals in their 20s and 30s but can also occur later in life progressively becoming more extensive. As this is a rare condition, the exact prevalence of this disease is not known.
Causes
This disease is inherited in an autosomal dominant pattern meaning a single defective gene can cause this condition. It can also develop without any family history as the result of sporadic changes. The mutation in the gene KRT5 is identified to be the cause of this disease which is essential for the production of a protein known as keratin 5. This family of protein is required for the structural framework of cells that particularly constitute the skin, hair and the nails. One of the functions of keratin 5 is the transfer of melanin pigmentation from melanocytes to keratinocytes. This transportation is essential for the normal skin coloration. The mutation in the KRT5 results in the decreased production of keratin 5 protein. Hence, the normal organization of the outer layer of the skin (epidermis) is impaired resulting in the various types of skin lesions. In individuals with this condition, when the mutation of KRT5 is not identified, the cause remains unknown.
Symptoms
This condition only affects the skin which can be itchy particularly in the heat of the summer time. Perspiration or friction also tends to aggravate the pigmentation. The abnormal skin condition usually begins in the armpits and the groin areas. Other sites can include the wrist, face, scalp, back of the hands, scrotum and the vulva. They may also have blackhead-like lesions on the face and the neck along with bumps that appear like the acnes. In addition, they may also develop cysts of the hair follicles on the scalp. This hyperpigmentation can occur over time but the skin lesions can progress to increase.
Diagnosis
The diagnosis of this disease is based on the features that are characteristic of this condition. In some cases, the skin biopsy may be required to evaluate the cause. Genetic testing can confirm the mutation in the gene that is responsible for developing this disease.
Treatment
There is no cure for this disease. Various types of treatments have been used, but most of them have not been very effective in eliminating the symptoms. Many types of topical creams and de-pigmenting agents have been tried in many of the cases. Topical steroids can be beneficial with the itchiness. Er-YAG laser treatment has been used for the removal of the rash between the breasts in a case, but the disease continued to develop in other untreated parts of the skin. This genetic disease does not appear to have any curative treatment.