Mild hypophosphatasia mimicking severe osteogenesis imperfecta in utero: bent but not broken.

We describe a fifth instance of hypophosphatasia presenting with prenatal findings suggestive of a very severe bone dysplasia but with a subsequently benign course. Spontaneous improvement of long-bone angulation began prenatally. The postnatal course has been encouraging. This sixth clinical form of hypophosphatasia, which we suggest should be called the benign prenatal form of hypophosphatasia, should be added to the differential diagnostic possibilities considered when angulation or bowing of long bones is discovered prenatally.