Poland Syndrome is a congenital disorder primarily characterised by the absence of the pectoral muscles on one side of the body.
During foetal development, ultrasound scanning at about four months may identify a deformity when limb and chest abnormalities are severe. A diagnosis, more so a correct one, is very unlikely at such an early stage.
How evident Poland Syndrome may be in a newborn child will depend very much on the severity of the case. While some babies may show dipping of the chest, a tight band of tissue running from the elbow to the armpit, and/or hand deformity, in other babies the condition may not be visible at all.
A baby displaying hand malformations as a feature of their Poland Syndrome will often receive some kind of diagnosis much earlier than those without, simply due to the disorder being more apparent. Correct diagnosis is dependant on whether the baby shows signs of chest deformities, and whether the nurse is aware of Poland Syndrome as an option. Approximately 1% of all live births have hand defects, the majority of which have nothing at all to do with Poland Syndrome.
Patients without hand involvement, particularly those with less severe chest anomalies, may not be diagnosed until later childhood or puberty, when chest and breast development brings about a more marked difference in the two sides of the body. This is particularly true for girls, who will likely notice severe asymmetrical development of the breasts. The majority of adolescent girls, even those without Poland Syndrome, will develop at different rates, and even fully developed women are unlikely to be completely symmetrical, meaning a slightly underdeveloped breast on one side of the body is not enough for a diagnosis and is actually very common. In the majority of cases where one breast is significantly smaller than the other, however, Poland Syndrome is the underlying cause.