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At a glance

It is a genetic disorder that belongs to a larger group of Acromesomelic Chondrodysplasia Syndrome (see “Other conditions to be considered”). It is characterized by complex brachydactyly and fibular hypoplasia.

Synonym

Fibular Hypoplasia Complex Brachydactyly Syndrome.

Incidence

Approximately 20 cases have been described in the literature.

Genetic inheritance

It is inherited as autosomal recessive trait. The responsible gene has been mapped to 20q11.2. Parental consanguinity is a risk factor. Mutations in the cartilage-derived morphogenetic protein 1 (CDMP1) gene have been reported in two acromesomelic chondrodysplasias (ie, Hunter-Thompson type and Grebe type) which are phenotypically related to DuPan Syndrome. CDMP1, a member of the transforming growth factor beta superfamily of secreted signaling molecules that regulate limb patterning and distal bone growth.

Pathophysiology

The cartilage-derived morphogenetic protein-1 (CDMP1) is crucial in the patterning of chondrogenesis, longitudinal bone growth, and appendicular skeleton. The genetic defect results in a missense substitution in the active domain of CDMP1, which leads to a change in the conformation and finally in the activity of CDMP1.

Diagnosis

Mainly clinical, based on the combination of short stature and limb malformations.

Clinical aspects

Patients affected with this syndrome present with short stature as a result of symmetrical limb malformations. In the upper limbs, the main findings are short metacarpal bones (especially the first metacarpals), short phalangeal bones (particularly the middle ones), and hypoplasia of the carpal bones. The thumbs are button-like, and all fingers tend to have radial deviation. In the lower limbs, the fibulas are either absent or severely hypoplastic, and the knees may be dislocated with hypoplastic and displaced patellae. The feet usually have an equinovalgus deformation associated with tibiotarsal dislocation of the ankle. The metatarsals are hypoplastic, as are the phalanges of all toes, which resemble ball-like remnants with hypoplastic nails. Intelligence and craniofacial features are normal.

Precautions before anesthesia

No particular precautions for this syndrome.

Anesthetic considerations

Careful padding and positioning are required to prevent dislocations of the joints. Because of the malformations, peripheral vascular access may be challenging.

Pharmacological implications

No specific implications for this condition.

Other conditions to be considered

  • Acromesomelic Dysplasia Types II (Hunter-Thompson) and III (Grebe): Extremely short stature as a result of acromesomelic dysplasia of the limbs (forearms, forelegs, hands, feet). In general, patients have normal intelligence. Joint dislocations may occur. There is normal craniofacial and axial skeleton upon examination.

  • Santos Syndrome (Fibular Agenesis, Hypoplasia, Oligodactylous Clubfeet, Anonychia, Nail Hypoplasia Syndrome): Characterized by fibular agenesis/hypoplasia, hypoplastic femora and grossly malformed/deformed clubfeet with severe oligodactyly, ungual hypoplasia/anonychia, sometimes associated ...

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