Nipples, Supernumerary

Rather extensive literature supporting dominant inheritance was reviewed by Gates (1946). Klinkerfuss (1924) found polymastia in 5 females in 4 generations. The extra breast consisted of a mass in one or both axillae which enlarged in pregnancy and lactation. In some, a nipple was associated with the adventitious breast tissue. It may have communicated with the main breast tissue because it swelled before nursing and shrunk with nursing. Pierre Marie (1893) also observed supernumerary breasts in 4 generations and noted an association with twinning. Weinberg and Motulsky (1976) reported a kindred in which 6 adult females in 2 generations showed bilateral accessory axillary breast without nipples or areolae. They concluded that the anomaly is probably caused by an autosomal dominant gene of variable expressivity which prevents normal regression of the embryonal mammary bridge. Without areolae or nipples, the trait is usually not detectable in prepubertal females and in males of all ages. Leung (1988) reported supernumerary nipples in a Chinese man and his identical twin daughters. The supernumerary nipples were situated below the normal nipples, which is usually the case in Caucasians. In Japanese women, according to Iwai (1907), 82% of instances of supernumerary nipples show a location above the normal breasts. An association with renal anomalies has been suggested (Meggyessy and Mehes, 1987). Rintala and Norio (1982) reported dysplastic divided nipples (intraareolar polythelia) bilaterally in a mother, her 2 daughters, and 1 son. By selective breeding in sheep, Alexander Graham Bell (1898) succeeded in producing 2 to 4 accessory nipples in 90% of the offspring. In the guinea pig this trait behaves as an autosomal dominant (Goertzen and Ibsen, 1951).

Toumbis-Ioannou and Cohen (1994) described polythelia in 3 sibs, 2 sisters and a brother. They tabulated reports of same in the English language literature starting with that by Iwai (1907). Multigeneration involvement was the rule. Urbani and Betti (1995) claimed that there is an association between familial polythelia and kidney and urinary tract malformations. In a subsequent report, Urbani and Betti (1997) reported an association between supernumerary nipples and Becker nevus (see 604919). They suggested this observation may be explained by the concept of paradominant inheritance proposed by Happle (1992) for Becker nevus. The idea of paradominant inheritance as described by Happle (1992) is that heterozygous gene carriers are usually phenotypically normal, and consequently the altered gene can be transmitted through multiple generations without phenotypic manifestation. Only when a somatic mutation occurs, resulting in a mosaic patch of cells homozygous for the mutation (or hemizygous), does a trait become evident.

Schmidt (1998) studied the prevalence, size, and predilections for sex and side of supernumerary nipples in a prospective clinical study. Of 502 individuals, 28 (5.6%) exhibited a supernumerary nipple, which was classified as small (areola only, diameter less than 30% of normal) in 21 persons and middle-sized (30 to 50% of normal) in 7 persons. The male/female ratio was 20 to 8 and the left/right side ratio was 15 to 7 in males and 5 to 4 in females. In 40% of individuals, one of the parents confirmed the presence of a supernumerary nipple. None of the 28 had a history of urinary tract infection or suspected urinary tract malformation.

Hundleby and Beighton (2007) described a South African woman with bilateral duplication of the nipples and areolae in an apparently horizontal plane without mammary tissue reduplication. The authors stated that this configuration of breast tissue had not previously been described. The family history was negative for any abnormalities of the breasts.