Mucin is not a rare finding in rosacea.

Mucin deposit is a feature that is not commonly mentioned in textbooks when talking about rosacea. Nevertheless, it is one of the prominent findings of a severe variant of the phymatous type of rosacea known as the fibrous type. We retrospectively investigated 20 cases of early stages of rosacea and examined the mucin deposit in them, with histochemical stains (Alcian Blue and Periodic Acid-Schiff). We found granulomas in 20% of these cases. Alcian Blue positive deposits of mucin were found in all cases with granulomas. The mucin was located in the granulomas (four cases) as well as in the infundibulum (one case). No deposits of mucin were evidenced in the dermis out of the granulomas, apart from the normal mucin of papillary and adventicial dermis. Periodic Acid-Schiff did not show any deposits in any case. Serologic lupus markers were negative in all patients with mucin deposits. We conclude that: (a) mucin is a common finding in granulomas of rosacea; (b) this mucin is probably not related to any progression to the mucinous variant of rhinophyma; (c) since discoid erythematosus lupus is a clinical differential of rosacea, it is important to be aware of the fact that mucin is a common finding in the granulomas, in order not to misdiagnose both entities.