Individual muscles or groups of muscles may be absent at birth. Muscle abnormalities can occur alone or as part of a syndrome.

Partial or complete agenesis of the pectoralis major is common and occurs alone or with ipsilateral hand abnormalities and various degrees of breast and nipple aplasia, as in Poland's syndrome. Poland's syndrome may be associated with Möbius' syndrome (paralysis of the lower cranial nerves, especially the 6th, 7th, and 12th), which has been linked to autism.

In prune-belly syndrome (see Congenital Renal and Genitourinary Anomalies: Prune-Belly Syndrome), ≥ 1 layers of the abdominal musculature are absent at birth; this often occurs with severe GU abnormalities, particularly hydronephrosis. Incidence is higher in males who often also have bilateral undescended testes. Malformations involving the feet and rectum also often coexist. Prognosis is guarded, even with early relief of urinary tract obstruction.

Treatment depends on severity of the condition and can range from minimal intervention to reconstructive surgery.

Last full review/revision January 2010 by Gregory S. Liptak, MD, MPH

Content last modified February 2012