Campomelic Dysplasia

Campomelic dysplasia is one of the more rare forms of congenital short-limb dwarfism. Its incidence is approximately 1 in 111,000 to 1 in 200,000 live births. The term "campomelic" or "camptomelic" is of Greek origin and literally means "bent limb."

 
How Campomelic Dysplasia Is Inherited

Campomelic dysplasia is typically inherited in a sporadic, autosomal dominant manner (3).

 
Causes of Campomelic Dysplasia

Campomelic dysplasia is caused by a mutation in the SOX-9 gene, localized to chromosome 17. The SOX-9 gene encodes for a transcription factor that is responsible for normal cartilage development and sexual development.

 
Physical Characteristics

Campomelic dysplasia is characterized by the bowing of the femur and tibia. Some individuals can have this condition without any appreciable bowing of the long bones but with other major features. These patients are referred to as having "acampomelic" camptomelic dysplasia. We will limit the following discussion to patients with classic campomelic dysplasia.

Campomelic dysplasia can be a lethal condition. However, a proportion of campomelic children can survive into adulthood. In the newborn period, respiratory distress may occur due to the lack of development of the cartilage rings that support the tracheobronchial tree. Although respiratory insufficiency may lead to hypoxic brain injury, in general patients with campomelic dysplasia have average intelligence.

Face & Skull:
  • Long and narrow skull
  • Prominent forehead
  • Flat face with a depressed nasal bridge
  • Micrognathism
  • Possible cleft palate
Trunk, Chest, & Spine:
  • Short neck with redundant skin at the nape of the neck
  • Small, narrow, and bell-shaped chest
  • Eleven pairs of ribs
  • Protuberant abdomen
Arms & Legs:
  • Anterior bowing of the femur and tibia.
  • A deep subcutaneous dimple over the most prominent aspect of
    the tibia.
  • Clubfeet, frequently present on both sides.
What are the X-ray characteristics?

The radiological features of campomelic dysplasia include bowing of the femur and tibia. Typically, patients exhibit delayed ossification of distal femoral and proximal tibial epiphyses. Radial heads are dislocated. Widely spaced vertical ischia and a hypoplastic pubic bone are seen in the pelvis. Vertebral pedicles are hypoplastic or nonmineralized. Cervical vertebrae are hypoplastic. The thorax is small and bell-shaped, with eleven ribs, appearing wavy and thin. The first metacarpals are short. Short middle phalanges of the second through fifth fingers are also typical (4).

 
Musculoskeletal Problems
Long Bone Bowing

Long bone bowing in campomelic dysplasia is variable. Corrective osteotomies of the femur and tibia should be performed so that the child can start standing and walking at the appropriate times. The timing of such surgery is influenced by the child’s respiratory status. Developmental milestones are delayed in campomelic dysplasia and this should be kept in mind during decision making. A period of casting is necessary in the immediate post-operative period, followed by long-term bracing to maintain correction.

Hip Dislocations

Congenital/developmental hip dislocations are typically managed along standard lines. In infancy, the mainstay of treatment is by means of a Pavlik harness. If this fails, surgery becomes necessary.

Cervical kyphosis is an initial problem, secondary to failure of formation of the anterior cervical vertebral bodies, which can lead to spinal cord compression. Thoracic kyphoscoliosis is a severe problem that may require surgery.

Clubfeet

Clubfeet should be treated along standard lines with corrective casting and surgery, depending upon the severity of the problem.

 
Problems Elsewhere in the Body
Tracheobronchial Tree

The most significant abnormality in campomelic dysplasia is the lack of development of the cartilage rings supporting the trancheobronchial tree. These cartilage rings normally keep the breathing passages open. Poor cartilage development may cause the collapse of these passages, producing extremely small airways and causing respiratory insufficiency.
At birth, the child may require a tracheostomy and long-term ventilation
at home for the first few years of life. Many do not survive past the neonatal period.

Congenital Heart Defects

Congenital heart defects were found in around 25% of cases. The most common anomaly is a patent ductus arteriosus or patent foramen ovale.
An echocardiogram should be done to evaluate for possible congenital heart disease.

Genitourinary Tract

Genitourinary Tract: Hydronephrosis (enlarged kidney), bilateral ureteral dilatation are seen in 1/3 of patients. Hypoplastic cystic kidney, renal hypoplasia, ureteral stenosis, and renal calculi have been described in the literature. These do not pose major health risks initially but require monitoring by a nephrologist/urologist in the long-term.

Sex Reversal

Some phenotypic females may genetically be males.

Hearing

Recurrent middle ear infections, poor development of bones that normally conduct sound (auditory ossicles) and abnormal skull shape are some of the factors that contribute to hearing loss. Any suspicion of hearing loss or recurrent ear infections should prompt referral to an ENT surgeon/ audiologist for further investigation.

 
What to Watch For
  • Respiratory distress in the newborn period.
  • Chromosomal analysis should be done to evaluate for possible sex reversal in phenotypic females.
  • A renal-pelvic ultrasound should be done to assess any anomalies of the genitourinary tract.
  • Cervical spine instability due to possible cervical kyphosis.
 
References
  1. Jones, Kenneth L. Recognizable Patterns of Human Malformation. Philadelphia, PA: Elsevier Saunders. 2006.
  2. Norman, EK. Pedersen, JC. Stiris, G. Van der Hagen, CB. 1993. Campomelic dysplasia-an underdiagnosed condition? European Journal of Pediatrics. 152: 331-333.
  3. Scott, Charles I. Dwarfism. Clinical Symposium, 1988; 40(1):21-24.
  4. Spranger, Jurgen W. Brill, Paula W. Poznanski, Andrew. Bone Dysplasias: An Atlas of Genetic Disorder of Skeletal Development. Oxford: Oxford University Press. 2002.

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