Congenital musculoskeletal anomalies are a group of defects caused by abnormal growth and/or development of the muscles, soft tissues, and/or bones.
Congenital anomalies may be classified as
Deformations
Malformations
A deformation is an alteration in shape due to unusual pressure and/or positioning in utero (eg, some forms of clubfoot) or after birth (eg, positional plagiocephaly—head flattening due to prolonged lying in one position). Some deformations resolve spontaneously within a few days, but others persist and require treatment.
A malformation is an error in normal organ or tissue development. Causes include chromosomal abnormalities, single-gene defects, teratogenic agents, or a combination of genetic and environmental factors; because of improved diagnostic and genetic analytic techniques, a decreasing number of cases are considered idiopathic.
Etiologies of congenital musculoskeletal anomalies may be genetic or due to prenatal environmental factors (eg, use of thalidomide, vitamin A).
Congenital musculoskeletal anomalies are common. They may involve only a single, specific site (eg, clubfoot) or be part of a syndrome of multiple congenital anomalies (eg, Walker-Warburg syndrome, which affects brain, muscle, and eye development). Careful clinical assessment may be necessary to distinguish an isolated anomaly from an atypical or mildly manifested syndrome.
Because of the large number of syndromes, the topics in this chapter are focused on the specific structural abnormalities. Detailed information on many of the specific syndromes is available from the Online Mendelian Inheritance in Man (OMIM) catalog of genetic disorders.
The anomalies discussed are
Genu valgum (knock-knees)
Genu varum (bowlegs)
Talipes equinovarus (clubfoot) and other congenital foot anomalies
In general, children with congenital musculoskeletal anomalies should be evaluated for other associated congenital anomalies and developmental delays. Identification of any underlying syndrome is important for prognosis and family counseling. A clinical geneticist should assess affected patients to establish a definitive diagnosis, including patients with an isolated congenital anomaly. Chromosomal microarray, specific gene tests, or broader gene panel tests should be considered in the evaluation of patients with congenital musculoskeletal anomalies. If the results of these tests are nondiagnostic, whole exome sequencing analysis may be recommended. Determining a diagnosis is essential for formulating an optimal treatment plan, providing anticipatory guidance and genetic counseling, and identifying relatives at risk of similar anomalies.
