Demonstration of polarizable crystals in fresh comedonal extracts: sebum crystallizes.

Previous studies using paraffin-embedded sections showed the presence of varying degrees of lipidic calculus (sebolith) formation in the pilosebaceous duct in acne comedonal lesions. The objective of this study was to examine the content of fresh acne comedonal extracts and pustules in polarizable crystalline material. Furthermore, to investigate if the amount of crystalline material correlates with the morphology, evolutionary stage, age and location of the comedone we performed polariscopic examination of 20 fresh acne comedonal extracts and 6 acne pustules. As controls, we used extracts from solar comedones, milia and epidermal inclusion cysts, follicular extracts from acne rosacea lesions, pustules of bacterial folliculitis and extracts from normal follicles from acne-prone individuals. The vast majority of acne comedones contained considerable amounts of polarizable crystalline material. Crystallization was more prominent in closed comedones, long-standing macrocomedones and conglobate comedones. Crystal formation was seen less commonly (p < 0.01) in solar comedones, milia and epidermal inclusion cysts. As shown in this study, crystallization of sebum is a common element of comedogenesis and may possibly contribute to comedo preservation.