An eponym that is little used (in the USA) for hypothyroidism (subnormal activity of the thyroid gland) that starts after birth and is manifest by features including delays in growth and development and myxedema surfacing during infancy. Myxedema is a dry waxy type of swelling, often with swollen lips and nose. Infantile hypothyroidism is synonymou [..]

1894 in the psychological sense; see infantile + -ism. Earlier in a physiological sense, "retarded and imperfect physical development," perhaps from French infantilisme (1871).

(n) an abnormal condition in which an older child or adult retains infantile characteristics(n) infantile behavior in mature persons

  A state marked by slow development of mind and body.

An obsolete term for various, often unrelated, disorders which consist of retention of the physical and/or psychological characteristics of infancy or childhood (Modern)

The permanent lack of Sexual Development in an individual. This defect is usually observed at an age after expected Puberty.

A fetish for dressing, acting, and being treated like an infant. This often requires practitioners to hire a dominatrix to serve as a "nanny."

the paraphilia of impersonating an infant and being treated as one by the partner--one of the stigmatic/eligibilic paraphilias. Synonym, autonepiophilia. See also adolescentilism; gerontalism; juvenil [..]