Hypotrichosis: Presence of less than the normal amount of hair. (Dorland, 27th ed)Desmogleins: A group of desmosomal cadherins with cytoplasmic tails that resemble those of classical CADHERINS.Hair Diseases: Diseases affecting the orderly growth and persistence of hair.Ichthyosis: Any of several generalized skin disorders characterized by dryness, roughness, and scaliness, due to hypertrophy of the stratum corneum epidermis. Most are genetic, but some are acquired, developing in association with other systemic disease or genetic syndrome.Hair: A filament-like structure consisting of a shaft which projects to the surface of the SKIN from a root which is softer than the shaft and lodges in the cavity of a HAIR FOLLICLE. It is found on most surfaces of the body.Scalp: The outer covering of the calvaria. It is composed of several layers: SKIN; subcutaneous connective tissue; the occipitofrontal muscle which includes the tendinous galea aponeurotica; loose connective tissue; and the pericranium (the PERIOSTEUM of the SKULL).Ectodermal Dysplasia: A group of hereditary disorders involving tissues and structures derived from the embryonic ectoderm. They are characterized by the presence of abnormalities at birth and involvement of both the epidermis and skin appendages. They are generally nonprogressive and diffuse. Various forms exist, including anhidrotic and hidrotic dysplasias, FOCAL DERMAL HYPOPLASIA, and aplasia cutis congenita.Consanguinity: The magnitude of INBREEDING in humans.Hypertrichosis: Excessive hair growth at inappropriate locations, such as on the extremities, the head, and the back. It is caused by genetic or acquired factors, and is an androgen-independent process. This concept does not include HIRSUTISM which is an androgen-dependent excess hair growth in WOMEN and CHILDREN.Nail Diseases: Diseases of the nail plate and tissues surrounding it. The concept is limited to primates.Hypohidrosis: Abnormally diminished or absent perspiration. Both generalized and segmented (reduced or absent sweating in circumscribed locations) forms of the disease are usually associated with other underlying conditions.Desmosomal Cadherins: A single-pass transmembrane glycoproteins that mediate CALCIUM-dependent CELL ADHESION and are core components of DESMOSOMES.Genes, Recessive: Genes that influence the PHENOTYPE only in the homozygous state.Pedigree: The record of descent or ancestry, particularly of a particular condition or trait, indicating individual family members, their relationships, and their status with respect to the trait or condition.Chromosomes, Human, Pair 18: A specific pair of GROUP E CHROMOSOMES of the human chromosome classification.Alopecia: Absence of hair from areas where it is normally present.Corneal Dystrophies, Hereditary: Bilateral hereditary disorders of the cornea, usually autosomal dominant, which may be present at birth but more frequently develop during adolescence and progress slowly throughout life. Central macular dystrophy is transmitted as an autosomal recessive defect.Hair Follicle: A tube-like invagination of the EPIDERMIS from which the hair shaft develops and into which SEBACEOUS GLANDS open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. (Stedman, 26th ed) Follicles of very long hairs extend into the subcutaneous layer of tissue under the SKIN.