Flexural Reticulate Hyperpigmentation Unmasking Dowling-Degos Disease: A Clinical and Histopathological Insight

Dowling-Degos disease (DDD) is a rare autosomal dominant genodermatosis characterized by progressive reticulate hyperpigmentation of flexural areas. We report the case of a 40-year-old woman who presented with gradually spreading lentiginous hyperpigmented macules involving the axillae, submammary folds, neck, and genital region. Clinical examination revealed no systemic associations, and dermoscopy showed seborrheic keratosis–like features with a characteristic fine reticular pigmented network. Histopathological examination confirmed the diagnosis of DDD, revealing elongated rete ridges, basal layer hyperpigmentation, and keratin-filled horn cysts. Although genetic testing was not performed, the diagnosis was supported by clinical, dermoscopic, and histological features. This case emphasizes the importance of recognizing the hallmark patterns of DDD to distinguish it from other pigmentary disorders such as acanthosis nigricans, lentiginosis syndromes, and neurofibromatosis. Management remains symptomatic and aimed at cosmetic improvement. Topical retinoids, hydroquinon and fractional laser therapies may offer partial benefit. Early diagnosis can reduce unnecessary investigations and guide appropriate counseling. A literature review is provided to support diagnostic and therapeutic decision-making in clinical practice.