Discussion
DDD is a rare autosomal dominant genodermatosis but can also occur sporadically. It is characterized by asymptomatic, progressive, reticulate hyperpigmented macules with a flexural distribution. Other cutaneous findings include comedo-like hyperkeratotic follicular papules on the neck, perioral pitted acneiform scars.5Loss-of-functional mutation in the keratin 5 (KRT5) gene on chromosome 12q13 is reported. Mutation of the gene results in disruption in melanosome transfer and trafficking. Gene locus mapping to chromosome 17p13.3 has also been reported. Other genes involved in pathogenesis of DDD are POGLUT1(protein O-glucosyltransferase 1) ,POFUT1 (protein O fucosyltransferase 1), and PSENEN (presenilin enhancer protein 2 gene).4
Epidermal cysts, multiple keratoacanthomas, squamous cell carcinoma, abscess, hidradenitis suppurativa, seborrheic keratosis, and pilonidal cysts are reported to be associated with DDD.2 These disorders are not present in our case and other family members. Histopathology of skin biopsy in classical DDD reveals thinning of the epidermis. Elongated, thinned, and branched (antler like) rete ridges with increased melanin pigmentation at their tips, but no increase in the melanocyte number.6 Histopathology of skin biopsy of our patient also revealed these classical findings. DDD with features of downs syndrome has not been reported till date in literature. Karyotyping in daughter would have revealed the association between DDD and downs syndrome.As the patient denied the intervention, association could not be established.
It is a rare genetic disorder and only few cases have been reported in our country. There is no definitive cure for Dowling-Degos disease. Different treatment options are depigmenting agents such as hydroquinone, retinoids and laser therapy such as fractional Erbium YAG laser.7
There is paucity of reported cases of DDD in literature. This condition should be kept in mind in the differential diagnosis of pigmented lesions of flexural sites.