Distichiasis

Fox (1962) reviewed the heredity of this anomaly. Dominant pedigrees were presented by Erdmann (1904) and by Cockayne (1933). Blatt (1924) traced double rows of eyelashes through 3 generations. See tristichiasis (190800). (The terms 'districhiasis' and 'tristrichiasis' refer to 2 or 3 hairs per follicle. Much confusion exists, however, and 'distichiasis' and 'districhiasis' are often used interchangeably to mean 'two rows of eyelashes.') In 3 generations of a family, Pico (1957) found 11 persons with congenital ectropion of whom 8 also had distichiasis. Two persons had distichiasis alone. Histologic study in 2 showed absence of Meibomian glands and replacement of the dense collagenous tissue of the tarsal plates by loose areolar tissue. The observation by Szily (1923) suggested recessive inheritance. Maumenee (1982) questioned the existence of mendelian distichiasis except as part of the syndrome of lymphedema with distichiasis (153400). Study of a family with both distichiasis and atypical serum cholinesterase indicated that the 2 traits are not closely linked (Shammas et al., 1976).

Howard and Wilson (1993) used the term pseudodistichiasis for the double row of eyelashes seen in association with anhidrotic ectodermal dysplasia (305100). They pointed out that the double row of eyelashes should not be confused with the misdirection of normal lashes referred to as trichiasis. A similar but distinct eyelash anomaly was reported in association with the Setleis forceps marks syndrome (227260) by Frederick and Robb (1992). In true distichiasis, a second row of eyelashes merges from the meibomian gland orifices; in pseudodistichiasis, the double row of eyelashes exit anterior to the meibomian orifices.