Background: The histopathological features of rosacea have not been described in detail.
Objective: To evaluate the histopathological features of rosacea according to clinical characteristics such as subtype and severity.
Methods: We retrospectively analyzed histopathological findings in 226 patients with rosacea, which included 52 patients with the erythematotelangiectatic rosacea (ETR) and 174 patients with the papulopustular rosacea (PPR) subtype. The frequency of each histopathological finding was compared between subtypes. Histopathological features were also compared according to the severity, through subgroup analysis within each subtype group.
Results: Perivascular and perifollicular lymphohistiocytic infiltration were common dermal findings in both subtype groups, but the intensity of dermal inflammatory infiltration was higher in PPR than in ETR. Follicular spongiosis and exocytosis of inflammatory cells into hair follicles were noted in both subtypes; but these findings were significantly more common in the PPR subtype. Vascular changes (telangiectasia and proliferation) and solar elastosis were common histopathological findings in both subtypes, with no difference in frequency between subtype groups. Demodex mites were identified in about 40% of patients, and the frequency of demodex mites did not differ between subtype groups. The intensity of perifollicular inflammation and the presence of follicular inflammatory reactions were dependent on the severity of rosacea in both subtype groups.
Conclusions: The intensity of inflammatory reactions, especially perifollicular infiltration, was higher in PPR patients than in ETR patients. Rosacea has a spectrum of histopathological features that are related to clinical progression between rosacea subtypes.