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Introduction to Birth Defects of the Face, Bones, Joints, and Muscles

By Simeon A. Boyadjiev Boyd, MD, Professor of Pediatrics and Genetics, Section of Genetics, Department of Genetics, University of California, Davis

Birth defects of the face and limbs are fairly common. They may involve only a specific body part, such as the mouth (cleft lip or cleft palate) or foot (clubfoot). Or they may be part of a genetic syndrome of many abnormalities, such as Treacher Collins syndrome, in which birth defects affect not only the face but also multiple other body parts.

Birth defects may be classified as

  • Deformities

  • Malformations

A deformity is a change in the shape of a body part. A deformity is caused by unusual pressure on the baby in the womb or the baby's position late during the pregnancy. Deformities are present in about 2% of births. Some deformities improve without treatment within a few days, but others need to be treated.

A malformation is an error in the baby's development that occurs in the womb. Causes of malformations include chromosome abnormalities, single-gene defects, and environmental factors (such as teratogens, which are substances known to cause birth defects). A malformation can also be caused by a combination of genetic and environmental factors. In some cases, the cause is unknown. About 3 to 5% of babies are born with a malformation.

Arthrogryposis multiplex congenita refers to a variety of joint and muscle problems that result from limited joint movement in the womb.

Craniofacial defects are caused by the abnormal growth or development of the head and/or facial bones while the baby is growing inside the mother. The most common defects of the face are cleft lip and cleft palate. Other defects may involve the ears, eyes, and jaw. Craniofacial defects that affect the skull include a skull that is too large (macrocephaly) or too small (microcephaly). Sometimes the bands of tissue that connect the bones of the skull (called sutures) close too early (craniosynostosis).

Hip and joint defects include developmental dysplasia of the hip and knee dislocation.

Limb defects are numerous. Sometimes a limb is missing or does not form completely. Part or all of the hand or foot may be missing. For example, the person may have too few or too many fingers or toes. Clubfoot (talipes equinovarus) is a defect in which the foot and ankle are twisted out of shape or position. Other foot defects include metatarsus adductus, metatarsus varus, talipes calcaneovalgus, and pes planus.

In bowlegs, the knees appear to be turned outward. In knock-knees, the knees appear to be turned inward. Other defects that affect the legs include twisting of the top part of the thighbone (femoral torsion) and twisting of the shinbone (tibial torsion).

Muscle defects may be present at birth. Babies can be born missing individual muscles or groups of muscles, or muscles can be incompletely developed. Defects in muscles can occur alone or as part of a syndrome.

Neck and back abnormalities can be caused by injuries to soft tissues or bones. Two of the most common abnormalities are

Spinal defects include scoliosis, which is rarely apparent at birth, and defects of a specific vertebra, which are likely to be identified at birth. A number of different genetic syndromes include scoliosis as one of their abnormalities. As children grow, the spinal curve caused by a defect of the spine can progress quickly. Doctors monitor the spine closely. The child may need to wear a brace or body jacket for up to 18 hours a day. Surgery may be needed.