4.2 Differential diagnosis
Differential diagnosis should include other deformities of the distal forearm (Langer 1965; Leiber & Olbrich 1981, 1135). Post-traumatic fusion of the ulnar aspect of the distal radial epiphysis may closely simulate the deformity of dyschondrosteosis, but Zweeloo Woman does not show any signs of such traumatic lesions.
Less commonly, infection may result in a similar deformity. The deformity is almost always unilateral in such cases. As is evident from all the published cases, dyschondrosteosis may be asymmetric as regards involvement, but, invariably, the criteria of dyschondrosteosis are radiologically observable, in both the forearms and the wrist regions (Langer 1965).
This is not a case of hypopituitary dwarfism, since it is not a generalised developmental failure. In achondroplasia, the most common form of skeletal dysplasia, the limbs are all shortened – the femur the most, then the humerus, then the bones of the lower legs and forearms. Adult stature rarely exceeds 140 cm (Aufderheide & Rodríguez Martín 1998, 360).
Achondrogenesis and thanatomorphic and camptomelic dysplasia are excluded from a differential diagnosis, because affected people die stillborn or at birth, and within the first year, respectively. Pseudoachondroplasia is also excluded as it is prominent at the hips (femora) and shoulder (humeri), with irregular epiphyses and widened metaphyses resulting in premature degenerative joint disease (Aufderheide & Rodríguez Martín 1998, 360-361).
Similarly, it is not a phocomelic type of dwarfism, since only a specific segment of each limb is involved and the skull is unaffected. The normal hands and feet argue against an effect of the ‘thalidomide injury’ type, for example following a viral infection. An ‘anti-Marfan’ type of syndrome can also be excluded, because the equivalent segment is involved in each limb, and the skull, hands and feet are spared (Langer 1965; Stoddart 1995, 9).