Trichilemmal cyst Trichilemmal cyst A trichilemmal cyst, also known as a wen, pilar cyst or isthmus-catagen cyst, is a common cyst that forms from a hair follicle. They are most often found on the scalp. The cysts are smooth, mobile and filled with keratin, a protein component found in hair, nails, skin, and horns. They are, however, clinically and histologically distinct from trichilemmal horns, which are much more rare and not limited to the scalp. Trichilemmal cysts may run in families and they may or may not be inflamed and tender, often depending on whether they have ruptured. Rarely, these cysts may
Protein domain Pfam database using the prefix DUF followed by a number, with examples being DUF2992 and DUF1220. There are now over 3,000 DUF families within the Pfam database representing over 20% of known families. "This article incorporates text and figures from George, R. A. (2002) "Predicting Structural Domains in Proteins" Thesis, University College London, which were contributed by its author." Protein domain A protein domain is a conserved part of a given protein sequence and (tertiary) structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can