Irregular Brown Lesions With Poorly Defined Borders in an Asymptomatic 15-Year-Old Patient

Confluent and reticulated papillomatosis (CRP) is a rare and often underdiagnosed disorder of keratinization that poses a significant clinical challenge due to its resemblance to more common pigmentary conditions, particularly acanthosis nigricans. Although first described more than 60 years ago, the pathogenesis of CRP remains incompletely understood. Recent microbiologic studies have identified an association between CRP and Dietzia species (family Dietziaceae; suborder Corynebacterineae; order Actinomycetales), implicating a potential bacterial trigger and providing a compelling explanation for the marked clinical response to antibiotic therapy. This emerging link represents a shift in understanding CRP from a purely keratinization disorder to a condition with a possible infectious component. We report a 15-year-old female with a one-year history of pruritic, brown hyperkeratotic papules on the abdomen and thorax, unresponsive to antifungals and topical corticosteroids. Histopathology revealed orthokeratosis, irregular acanthosis, papillomatosis with digitiform projections, compact hyperkeratosis, focal parakeratosis, and mild basal hyperpigmentation without atypia. Differential diagnoses included Cushing’s disease, Pityrosporum infection, and cutaneous amyloidosis. A skin biopsy confirmed CRP, which typically presents as verrucous or hyperkeratotic papules coalescing into plaques with a peripheral reticulated pattern. While oral minocycline is the traditional treatment, azithromycin offers a safer, effective alternative. Emerging evidence links Dietzia species to CRP, highlighting the importance of recognizing this association for accurate diagnosis and optimized antimicrobial therapy.