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Condition report · Musculoskeletal

Campomelic Dysplasia

Whole genome sequencing reads the SOX9 gene for changes that cause campomelic dysplasia, a severe skeletal condition in which the long bones of the legs are bowed and breathing can be difficult.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

A severe skeletal condition in which the long bones of the legs are bowed, often with breathing difficulties and, in genetic males, differences of sex development. It is caused by changes affecting one copy of the SOX9 gene.

Campomelic dysplasia is a rare and severe skeletal condition. Its name comes from Greek words meaning bent limb, and affected babies are usually born with the long bones of the legs bowed. Other features can include a small jaw with a cleft palate, club feet, underdeveloped shoulder blades and only 11 pairs of ribs. Soft, narrow airways often cause breathing difficulties, and many affected babies do not survive the newborn period. In people who are genetically male, about three quarters have female or ambiguous genitalia.

The condition is caused by changes affecting one copy of the SOX9 gene. SOX9 is a transcription factor, a protein that switches other genes on or off, and it is especially important for the development of the skeleton and for determining sex before birth. In most cases, one copy has lost its function.

Most cases arise new, so parents are not typically affected, although a few adults have been diagnosed after an affected child was born. Parental mosaicism has been reported, so genetic counselling and parental testing help clarify recurrence risk. Care focuses on breathing and feeding in infancy, and on spine, hip, hearing and hormone checks for children who survive the newborn period.

The condition we analyse

Autosomal dominant

Caused by changes in one copy of SOX9, a gene that controls cartilage, bone and testis development; in most cases one copy has lost its function. Most cases arise de novo.

Signs and symptoms

Bowing of the thigh and shin bones, small shoulder blades, a small jaw with cleft palate, club feet and only 11 pairs of ribs. Soft, narrow airways commonly cause breathing difficulties, and many affected babies die in the newborn period. About three quarters of affected genetic males have female or ambiguous genitalia. Those who survive infancy may develop curvature of the spine, short stature or hearing loss.

What a diagnosis changes

Care focuses on breathing and feeding support in infancy, with orthopaedic, hearing and spine monitoring for those who survive the newborn period. Endocrine assessment is needed when sex development is affected. Most cases arise de novo, but parental mosaicism has been reported, so genetic counselling and parental testing guide recurrence risk.

Genes analysed

Also known as

acampomelic campomelic dysplasia; campomelic dwarfism; Campomelic Syndrome; CMD; CMPD1

MONDO:0007251OMIM 114290Orphanet 140MedGen 354620Sources: [1][3][2]

Why whole genome sequencing

Campomelic dysplasia usually arises from a new change, but a family history can still shape the advice for relatives. Whole genome sequencing reads the SOX9 gene in the same test.

Most cases are new in the family

Most cases arise from a new change in SOX9 rather than one inherited from a parent. Parental testing and genetic counselling help clarify the risk to future pregnancies, and prenatal testing is possible once the family's change is known.

Spine and hearing checks continue

Children who survive infancy need annual monitoring of spinal curvature, and hearing aids are used where there is hearing impairment. Hip problems and clubfeet are treated using standard protocols.

References

  1. Unger S, Scherer G, Superti-Furga A, 2008. Campomelic Dysplasia. GeneReviews
  2. Campomelic dysplasia. MedlinePlus Genetics
  3. Haseeb A, Kc R, Angelozzi M, de Charleroy C, Rux D, Tower RJ et al., 2021. SOX9 keeps growth plates and articular cartilage healthy by inhibiting chondrocyte dedifferentiation/osteoblastic redifferentiation. Proceedings of the National Academy of Sciences of the United States of America

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