- 1 in 20,000 births.
- In 50% of cases there are transverse reduction deficiencies of one forearm or hand without associated anomalies.
- In 50% of cases there are multiple reduction deficiencies and in 25% of these there are additional anomalies of the internal organs or craniofacial structures.
- Amputation of the upper extremity is usually an isolated anomaly, whereas amputation of the leg or bilateral amputations of all limbs are usually part of a genetic syndrome.
- Isolated amputation of an extremity can be due to amniotic band syndrome, exposure to a teratogen or a vascular accident.
- If the defect is unilateral, it may correspond to the femur–fibula–ulna or femur–tibia–radius complex. The former is non-familial, while the second has a strong genetic component.
- Hands and feet are present (may be normal or abnormal), but the intervening arms and legs are absent.
- Three syndromes must be considered in the differential diagnosis of phocomelia:
- Roberts syndrome: autosomal recessive; tetraphocomelia, bilateral facial cleft, micrognathia, hypertelorism, ear and nose malformations.
- Thrombocytopenia with absent radius (TAR) syndrome: autosomal recessive; absence of radius bilaterally associated with thrombocythopenia,
- Grebe syndrome: autosomal recessive disorder described in the inbred Indian tribes of Brazil. Characterized by marked hypomelia of upper and lower limbs, increasing in severity from proximal to distal segments. In contrast to Roberts syndrome, the lower limbs are more affected than the upper extremities.
Congenital short femur:
- Classified into five groups:
- Simple hypoplasia of the femur
- Short femur with angulated shaft
- Short femur with coxa vara: this is the most common and is due to deformity of the hip, whereby the angle between the head and the shaft of the femur is reduced to less than 120 degrees.
- Absent or defective proximal femur.
- Absent or rudimentary femur.
- One or both femurs can be affected but the right one is more frequently involved.
- Femoral hypoplasia–unusual facies syndrome, which is sporadic, consists of bilateral femoral hypoplasia and facial defects, including short nose with broad tip, long philtrum, micrognathia and cleft palate.