CLINICAL, MORPHOLOGICAL AND IMMUNOHISTOCHEMICAL CHARACTERISTICS OF SKIN DYSCHROMIAS

Abstract

Background: Acquired macular hyperpigmentations – persistent dyschromic erythema (PDE), pigmented lichen planus (PLP) and idiopathic eruptive macular pigmentation (IEMP) – are common dermatological conditions with poorly understood etiopathogenesis and difficult differential diagnosis. Objective: To study clinical, pathomorphological and immunohistochemical features of PDE, PLP and IEMP for optimizing differential diagnosis. Methods: 120 patients (16–75 years) were examined (30 each with PDE, PLP, IEMP and post-inflammatory hyperpigmentation as control). Skin biopsies were evaluated histologically (hematoxylin-eosin) and immunohistochemically using antibodies against CD8, CD68, CD207/Langerin and p16. Results: PDE presented with large >5 cm patches on neck/back with peripheral erythema (67%); PLP – with 0.5–5 cm patches on scalp/neck/folds and pruritus (100%); IEMP – with small 0.5–2 cm asymptomatic patches on trunk/limbs. Histologically, PDE showed lichenoid interface dermatitis in early stage and superficial perivascular dermatitis in late stage; PLP – vacuolar interface dermatitis with apoptosis; IEMP – non‑specific perivascular dermatitis without basal layer damage. Immunohistochemically, PLP was characterized by high expression of p16 (100%) and CD8 (100%); PDE and IEMP by expression of CD68 (67% and 100% respectively) and CD207/Langerin (67% and 67%). Conclusions: Combined clinical‑morphological and immunohistochemical assessment allows reliable differentiation of PDE, PLP and IEMP. p16/CD8 are specific markers for PLP, while CD68/CD207 for PDE/IEMP.