PRRT2 and Down syndrome: The most frequent were as follows: the Williams‐Beuren 7q11.23 deletion syndrome (five patients), 15q11.2 duplication syndrome, distal (three patients), 16p11.2 duplication syndrome including PRRT2 (four patients), the Potocki‐Lupski 17p11.2 duplication syndrome (two patients), and 17p13.3 deletion syndrome, also known as Miller‐Dieker lissencephaly deletion syndrome (three patients).