Editor—The small patella syndrome (SPS, *MIM 14789), also known as ischiopatellar dysplasia, coxopodo patellar syndrome, or Scott-Taor syndrome, is a rare autosomal dominant disorder, characterised by a/hypoplasia of the patellae and various anomalies of the pelvis and feet. This syndrome was first described by Scott and Taor1 in 1979 in a large family with bilateral small or absent patellae accompanied by anomalies of the pelvic girdle and upper femora in most of the affected subjects. To our knowledge, 42 patients have been reported with this disorder,1-9comprising 35 cases from five families and seven sporadic cases. This bone dysplasia is characterised by patellar a/hypoplasia and pelvic anomalies, including bilateral absent or delayed ossification of the ischiopubic junction and infra-acetabular axe cut notches. Other major signs are a wide gap between the first and second toes, short fourth and fifth rays of the feet, and pes planus. Various other skeletal anomalies have been reported, such as elongated femoral necks, flattened and widened proximal femoral epiphyses, hypoplasia of the lesser trochanter, and tarsal anomalies. SPS should be clinically differentiated from disorders with a/hypoplastic patellae, in particular the autosomal dominant disorders isolated familial patella aplasia-hypoplasia (PTLAH) syndrome10 and the more severe nail-patella syndrome (NPS).11 The latter is caused by mutations of the LMX1B gene on chromosome 9q34. Recently, a locus for PTLAH has been identified on chromosome 17q21-22. As yet, it is unknown whether SPS and PTLAH are allelic disorders. Here we report on five cases from three families with SPS, compare their clinical and radiological anomalies with those of previously reported cases, and propose minimal diagnostic criteria for SPS. Given the clinical overlap between SPS, PTLAH, and NPS, we have studied the possible involvement of candidate regions for these syndromes on chromosome 17q21-22 and 9q34, respectively, …