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Medical Author:

John Mersch, MD, FAAP

John Mersch, MD, FAAP

Dr. Mersch received his Bachelor of Arts degree from the University of California, San Diego, and prior to entering the University Of Southern California School Of Medicine, was a graduate student (attaining PhD candidate status) in Experimental Pathology at USC. He attended internship and residency at Children's Hospital Los Angeles.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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What is Poland syndrome?

First described by the 19th-century British anatomist Sir Alfred Poland, Poland syndrome is a unique pattern of one-sided malformations that are present at birth (congenital malformations). Poland syndrome is noted for the underdevelopment or absence of the chest (pectoralis) muscles on one side of the body as well as webbing of the fingers (cutaneous syndactyly) on the hand of the same side (ipsilateral side) of the body.

Can Poland syndrome affect either side of the body?

Yes. For reasons not understood, Poland syndrome is twice as likely to involve the right side of the body.

How frequent is Poland syndrome?

The severity of Poland syndrome is variable, and it is possible for mild cases not to be evident until puberty when breast tissue and chest muscle mass development become more obvious. It is felt, therefore, that cases may be misdiagnosed and underreported. Experts currently are reporting an incidence of one in 10,000 to one in 100,000 live births. For reasons not appreciated, boys are more likely than girls to have Poland syndrome.

What causes Poland syndrome?

The cause of Poland syndrome is not known. The disorder is currently considered "a nonspecific developmental field defect" occurring at about the sixth week of fetal development. Diminished blood flow through the subclavian artery that supplies blood to the arm has been blamed, but final proof for this idea is lacking. Speculation has involved two hypotheses. One proposes that the underlying ribs on the affected side grow too quickly in a forward growth plane and thus reduce the flow of blood in the arteries leading to the overlying pectoralis muscle and arm on the affected side. Another proposal is that a malformation of the embryonic blood vessel serving the pectoralis muscle and arm/hand on that side of the body limits blood flow to these structures. To date no animal research has provided conclusive support for these proposals.