Medically called athelia, this is a rare condition
but it is common in certain conditions. Athelia tends to occurs on one side (unilaterally)
in children with the Poland sequence and on both sides (bilaterally) in certain
types of ectodermal dysplasia.
T he Poland sequence (named for Alfred Poland, a celebrated 19th-century British
surgeon and ophthalmologist) is a unique pattern of one-sided malformations characterized
by a defect of the chest (pectoralis) muscle on one side of the body and webbing
of the fingers (cutaneous syndactyly) of the ipsilateral hand (the hand on the same
side). It is right-sided three times more often than it is left-sided. The disorder
is currently considered "a nonspecific developmental field defect" occurring at
about the sixth week of fetal development. The cause is uncertain. In Poland syndrome
there is aplasia of the sternal head of the pectoralis major: the end of the main
chest muscle that normally attaches to the breastbone is missing. On that side of
the body, nearby chest muscles (the serratus anterior and latissimus dorsi muscles)
may also be absent as may be the armpit (axillary) hair. In girls, the breast on
that side is also usually absent (amastia) and there is no nipple. There is athelia.
Ectodermal dysplasia is not one but a number of hereditary conditions usually
characterized by the abnormal development of skin, absence of sweat glands, dry
eyes and abnormal development of teeth -- all structures derived from the ectoderm
(the outside layer in early embryonic development). The absence of sweat glands
leads to an inability to sweat and heat intolerance.
Athelia also occurs in association with the progeria (premature aging) syndrome
and the Yunis-Varon syndrome (a multiple congenital malformation first reported
in 1980).
Athelia is distinguished from amastia, wherein the breast is absent, and from
amazia, wherein breast tissue is absent but the nipple is still resent.
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