Autism spectrum disorder (ASD) and achondroplasia are two distinctive disorders. Co-occurrence of ASD with different monogenic disorders, chromosomal aberration, and molecular defined syndromes has been reported. Yet, the coexistence of ASD with achondroplasia has been recently reported; it was supposed to be merely coincidental. It is of particular interest herein to report on an Egyptian patient having achondroplasia and ASD simultaneously. The current report includes a comparison of both cases and throws light on the importance of genetic and environmental contributions in the etiology of ASD.