A Report of Two cases of Al-Awadi Raas-Rothschild Syndrome (AARRS) supporting that “Apparent” Phocomelia differentiates AARRS from Schinzel Phocomelia Syndrome (SPS)

Although there is a long list of syndromes with phocomelia, there are only two syndromes in which there is concurrent pelvic dysplasia and phocomelia: Al-Awadi–Raas-Rothschild syndrome (AARRS) and Schinzel phocomelia syndrome (SPS). Currently, there is a diagnostic confusion between the two syndromes and both have the same MIM entry (MIM 276820). We believe that the two syndromes are different entities and we also believe that the limb defect in SPS is a “true” phocomelia while the limb defect in AARRS is an “apparent” phocomelia. “Apparent” phocomelia describes the most severe form of ulnar ray deficiency in which there is absent ulna with radio-humeral synostosis. “Apparent” phocomelia is diagnosed radiologically by three radiological features: the apparently single bone occupying the arm/forearm appears relatively long, the area of radio-humeral synostosis will have thicker cortex with or without slight angulation, and the lower end of the bone resembles the lower end of a radius and not a humerus. In this paper, we present two new cases of AARRS from two different Saudi Arabian tribes: one case with R292C mutation of WNT7A with bilateral “apparent” phocomelia and a second case with a novel c.814G>T mutation of the WNT7A gene (resulting in wnt7a protein truncation at position 272) with unilateral “apparent” phocomelia. We reviewed previously reported cases of AARRS and SPS to further delineate the differences between these two syndromes. We make the argument that these two syndromes are two different entities and hence require two different MIM entries.