Ear hair canal is sometimes trimmed for cosmetic reasons. Excessive hair growth within or on the ear is known medically as "auricular hypertrichosis". Some men, particularly in the male population of India, have coarse hair growth along the lower portion of the helix, a condition referred to as "having "hairy pinnae"" ("hypertrichosis lanuginosa acquisita"). Hair is a protein filament that grows from follicles in the dermis, or skin. With the exception of areas of glabrous skin, the human body is covered in follicles which produce thick terminal and fine vellus hair. It is an important biomaterial primarily composed of protein, notably keratin.
MPLKIP of the hairs. Only a minority of the TTD cases carry a MPLKIP defect: more frequently, the gene ERCC2 is mutated, which encodes a subunit of the protein complex TFIIH that is required for general transcription and for nucleotide excision repair of DNA damage. MPLKIP M-phase-specific PLK1-interacting protein (TTD non-photosensitive 1 protein) is a protein that in humans is encoded by the MPLKIP gene (previously known as C7orf11). Patients with an inherited defect in both alleles of the gene suffer from trichothiodystrophy (TTD), a disease hallmarked by brittle hair and nails and usually by developmental difficulties as well. One patient