Proximal femoral focal deficiency (PFFD) and fibular A/hypoplasia (FA/H): a model of a developmental field defect.

Proximal femoral focal deficiency (PFFD) and fibular a/hypoplasia (FAH) are distinct malformations of the lower limbs. Both can occur as isolated defects or in association with other limb malformations. In fact, fibular defects frequently are present in PFFD, and, conversely, femoral abnormalities can be found in the presence of a typical FAH picture. We report on 5 patients with a variable combination of femoral and fibular defects. In one of them unilateral PFFD was associated with lateral foot defects, in the absence of fibular abnormalities, and with a phenotype similar to that observed in the femoral hypoplasia/unusual face syndrome (FH/UFS). Another patient had isolated PFFD on one side, with controlateral absence of femur, fibula, and tibia. Another patient had a PFFD, fibular hypoplasia, and abnormalities of fibular foot rays, and the last 2 patients, a father and son, had, respectively, bilateral foot malformations plus fibular and tibial hypoplasia in the father and a PFFD in the son. These observations represent a further demonstration of the existence of a fibular developmental field, and contribute to the definition of its spatial boundaries. The variable involvement of elements comprised in the developmental field can be explained by multifactorial etiology.