Athelia is a condition in which one or both nipples are absent. This is a congenital condition, which means that it is present from birth. It is not possible to develop athelia later in life, and the loss of one or both nipples because of accident, disease or surgery is not considered athelia.
A rare condition, athelia is a birth defect that can develop during the first trimester. During the sixth week of gestation, a growing fetus begins to develop mammary glands, and if these do not mature normally, the baby might be born with athelia. The occurrence of this condition can also be traced to the period immediately before or after birth, because the nipples develop out of the breast tissue at this time. Occasionally, an infant might be born with amastia, which is the lack of all breast tissue on one or both sides, including the absence of the nipple.
Though athelia itself might be considered a benign condition, women missing nipples on both sides will be unable to breastfeed. If the condition is an isolated anomaly, this is the most serious problem for people with the condition. Athelia is, however, linked to a number of more serious diseases, including Poland sequence, ectodermal dysplasia and Yunis-Varon syndrome, all of which are congenital.
In Poland sequence, the chest muscle is deformed or missing on one side of the body, which effects the development of nearby muscles and the hand on the same side. Often, infants born with this condition are missing ribs and show increased webbing between the fingers, which impairs motor ability. In girls, the breast and nipple on the affected side are usually absent. This disorder is classified as a nonspecific developmental field defect, and as such, there is no known cause. Poland sequence is a rare condition that affects the right side of the body nearly twice as often as the left.
A problem in the development of the ectoderm can cause athelia in people who are affected by ectodermal dysplasia or Yunis-Varon syndrome. The ectoderm is the outer layer of a very young embryo and later turns into the skin, nervous system, teeth and sweat glands. If the ectoderm fails to develop properly, these parts of the body might show abnormalities. The nipple, which is a modified sweat gland, might be absent on one or both sides in people affected by either of these conditions.