Merck Manual

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Congenital Muscle Abnormalities


Simeon A. Boyadjiev Boyd

, MD, University of California, Davis

Reviewed/Revised Sep 2022
Topic Resources

Individual muscles or groups of muscles may be absent or incompletely developed 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 syndrome. Poland 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 Prune-Belly Syndrome (Triad Syndrome) Prune-belly syndrome consists of abdominal muscle deficiency, urinary tract abnormalities, and intra-abdominal undescended testes. The name prune-belly syndrome derives from the characteristic... read more Prune-Belly Syndrome (Triad Syndrome) , more than one layer of the abdominal musculature is absent at birth; this often occurs with severe genitourinary abnormalities, particularly hydronephrosis. Incidence is higher in males who often also have bilateral undescended testes Cryptorchidism Cryptorchidism is failure of one or both testes to descend into the scrotum; in younger children, it is typically accompanied by inguinal hernia. Diagnosis is by testicular examination, sometimes... read more Cryptorchidism . Malformations involving the feet and rectum also often coexist. Prognosis is guarded, even with early relief of urinary tract obstruction.

Chromosomal microarray analysis Diagnosis Chromosomal abnormalities cause various disorders. Abnormalities that affect autosomes (the 22 paired chromosomes that are alike in males and females) are more common than those that affect... read more , specific gene tests, or broader gene panel tests should be considered in the evaluation of patients with congenital musculoskeletal abnormalities. If the results of these tests are nondiagnostic, whole exome sequencing analysis is recommended.

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

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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