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Muscle Defects

By

Simeon A. Boyadjiev Boyd

, MD, University of California, Davis

Last full review/revision May 2020| Content last modified May 2020
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Topic Resources

Babies can be born missing individual muscles or groups of muscles, or muscles can be incompletely developed.

Birth defects of the muscles can occur alone or as part of a syndrome.

The pectoralis major muscle (the major muscle in the chest, sometimes called the "pecs" in adults) can be partly developed or missing altogether. This defect can occur alone or with various hand, breast, or nipple abnormalities, as in Poland syndrome. The cause of most of these types of muscle disorders is unknown.

One or more layers of the abdominal muscles may be missing at birth, as in prune-belly syndrome. In this disorder, the missing layers of abdominal muscles cause the abdominal wall to have a wrinkled appearance, the testes do not descend into the scrotum (cryptorchidism Undescended testes Undescended testes (cryptorchidism) are testes that remain in the abdomen or the groin instead of descending into the scrotum. Retractile testes (hypermobile testes) have descended into the... read more Undescended testes ) in boys, and/or urinary tract defects develop. The cause of prune-belly syndrome is not clear.

After birth, doctors can identify the defects during a physical examination.

Treatment of Muscle Defects

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Test your knowledge

Preventive Health Care Visits in Infants
Frequent doctor visits are recommended for all infants younger than 1 year of age. These visits, also called well-child visits, make it possible to check development, look for health problems, provide age-appropriate vaccinations, and educate parents. Which of the following is a condition that might affect some infants born very prematurely, with less than 32 weeks of development in the uterus?
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