The association of photo-induced collagen degeneration and the development of telangiectasias in rosacea

Rosacea is a chronic, often progressive disorder characterized by facial erythema, telangiectasias, papules, pustules, and/or rhinophyma. In this study, we investigated the tissue structure in rosacea compared to controls. We performed a case–control study between five patients with mild-to-moderate erythematotelangiectatic rosacea (ETR) and five matched controls. Facial biopsy samples from rosacea patients and controls were stained with picrosirius red for collagen and CD31 for microvessel identification. Mean collagen content was significantly greater in control samples (19.603% ±8.821%) compared to rosacea samples (16.812% ± 7.787%, p = 0.030). In contrast, mean microvessel density was significantly higher in rosacea patients (4.775 E-5 ± 1.493 E-5 µm⁻³) compared to controls (2.559 E-5 ± 8.732 E-6 µm⁻³, p = 0.004). Mean microvessel lumen area was also significantly higher in rosacea patients (491.710 ± 610.188 µm²) compared to controls (347.879 ± 539.624 µm², p = 0.003). We identified a correlation between decreased collagen content and increased microvessel size and density in rosacea patients that was not observed in controls. These structural changes to the dermal matrix may contribute to the characteristic vessel growth and dilation in rosacea.