Pseudoachondroplasia (PSACH) is a relatively common osteochondrodysplasia characterized clinically by short-limbed short stature with normal face, and radiographically by platyspondyly and dysplasias of epiphyses and metaphyses of the tubular bones. Recently, mutation of cartilage oligomeric matrix protein has been identified in PSACH. However, clinical variability and genetic heterogeneity have been reported in PSACH, indicating a possible existence of a second PSACH gene. Here, we report on a patient with a typical severe form of PSACH who had a de novo interstitial deletion in the long arm of chromosome 11 [del(11)(q21q22.2)]. The size of the deletion was estimated at 0.8-7.3 Mb using fluorescent in situ hybridization (FISH). This deletion may contain or disrupt a second PSACH locus.