Clinical, Dermoscopic, Histopathological, and Immunohistochemical Correlation in Nonmelasma Diffuse Facial Melanosis: A Descriptive Cross-sectional Study from a Tertiary Care Hospital

Background: Diffuse facial melanosis (DFM) is a common pigmentary disorder affecting individuals of all ages. Conditions in this category include pigmented contact dermatitis (PCD), lichen planus pigmentosus (LPP), and ashy dermatosis (AD), which fall under the umbrella term acquired dermal macular hyperpigmentation, as well as other diseases. These disorders impose a significant psychological burden and present a complex clinical challenge. Aim: This study aims to evaluate and correlate the clinical, dermoscopic, histopathological, and immunohistochemical patterns of acquired pigmentary DFM in patients older than 12 years. Methods: This descriptive cross-sectional study was conducted in the pigmentary clinic between August 2022 and January 2024. Patients above 12 years of age with DFM were enrolled, and evaluation was done by clinical, dermoscopic, histopathological, and immunohistochemical analysis. A statistical correlation was performed on the above findings. Results: A total of 110 patients, aged between 17 and 65 years, were included in the study. PCD was the most common disorder (31.82%), followed by LPP (26.36%), exogenous ochronosis, and AD. The most common medical conditions included nonalcoholic fatty liver disease (8.18%) and hypothyroidism (7.27%). Pigmentation was the chief complaint in all cases, followed by scaling and itching. Dermoscopy revealed features such as globules or dots of varied colors, a pseudoreticular pattern, pigment network, and pinkish hue across different types of melanoses. Specific patterns such as the owl’s-eye, hem-like, worm-like, and wagyu beef-like patterns were also noted. Histopathological analysis showed features of pigment incontinence, perivascular infiltrate, and increased basal pigmentation in most disorders. Immunohistochemical analysis revealed positivity for CD4, CD8, and Melan-A, which correlated with the histopathological findings. Limitations: These include selection bias and interobserver variability in dermoscopic and histopathological findings, as well as smaller sample sizes in some cases of facial melanosis, and limitations of immunohistochemical analysis. Conclusion: A combined approach involving clinical, dermoscopic, histopathological, and immunohistochemical diagnosis can aid in more accurate diagnosis of this challenging entity and a deeper understanding of its molecular pathology.