Clinical, metabolic, dermoscopic, and reflectance confocal microscopy features of prurigo pigmentosa: a retrospective case series

Background Prurigo pigmentosa (PP) is a chronic, recurrent inflammatory dermatitis with nonspecific stage-dependent clinical features, leading to misdiagnosis. Noninvasive imaging may complement clinical and histopathological assessment. Metabolic abnormalities have been reported in PP, although their clinical significance remains unclear.Objectives To characterize the clinical, metabolic, dermoscopic, and reflectance confocal microscopy (RCM) features of PP and reduce misdiagnosis.Methods We retrospectively reviewed patients with histopathologically confirmed PP and available metabolic screening data from July 2020 to April 2026. Clinical, dermoscopic, RCM, laboratory, treatment, and follow-up data were extracted from medical records.Results Nine women aged 17–33 years had seasonal eruptions (June–September). Seven reported dietary triggers, including caloric restriction in four and ketogenic diets in three. Disease duration ranged from 0.5 to 37 months, with initial misdiagnoses as eczema or contact dermatitis. Metabolic abnormalities included dyslipidemia (n=8), type 2 diabetes (n=3), elevated urinary ketones (n=3), hepatic steatosis (n=7), and elevated body mass index (n=7). Lesions were classified as early (n=3), fully developed (n=5), and late stage (n=1). Dermoscopy identified punctate, linear, and reticular vascular patterns with granular, patchy, or honeycomb-like brown pigmentation. RCM revealed epidermal spongiosis, basal cell degeneration, melanophage infiltration, and dermal inflammatory infiltrates.Conclusion Nonspecific features and coexistence of lesions at different stages contribute to diagnostic difficulty. Dermoscopy and RCM may provide complementary noninvasive information for clinical and histopathological evaluation. Metabolic screening may be considered in patients with recurrent disease, dietary triggers, elevated BMI, ketonuria, or suspected lipid/glucose metabolism abnormalities.