Clinical Characteristics

Most individuals had intellectual disability (18/19) varying from mild (8/19) to mild/moderate (3/19), moderate (3/19) and severe (2/19). Abnormal behavior was observed in many cases (14/19) and included attention-deficit/hyperactivity disorder (ADHD) (10/19) or autism spectrum disorder (4/19). Additional behavioral concerns included anxiety, aggressiveness, and auto-mutilation. Dysmorphic features and skeletal anomalies were noted in many cases. They included mild facial dysmorphism, but this feature was nonspecific and thus not consistent with a clinically recognizable syndrome. Noteworthy, sagittal craniosynostosis with scaphocephaly was observed in two unrelated cases and oxycephaly with synostosis of the sagittal, metopic and coronal sutures in a third unrelated case. Moreover, multiple diffuse osteochondromas were present in two brothers and in one girl from an unrelated family. Interestingly, several of the osteochondromas that were initially detected in one patient at 4 years of age were no longer detected on X-rays or were no longer palpable two years later. The girl had no complaints of pain, and she ran and played without difficulty.