As the affected individuals in family C exhibit a similar clinical profile and molecular diagnosis to the previously described cases with homozygous PTCs in PDZD8 (Table 1), they constitute the fifth and sixth individuals and the third family diagnosed with IDDADF resulting from mutation of PDZD8. Examination of the clinical features shared by all six known cases of IDDADF revealed a core clinical phenotype of developmental delay, ID, autism, and facial dysmorphism (Table 1). Here, PDZD8 is linked to autism.