UBE2E2 and RIDDLE syndrome: WES identified two novel variants: c.62 A > G: p.(D21G) in STUM, and c.122 A > C: p.(E41A) in UBE2U. Of interest, UBE2U has been reported to regulate RNF168 [22], an E2-ubiquitin conjugating enzyme that has been associated with the Radiosensitivity Immunodeficiency Dysmorphic features and Learning difficulties (RIDDLE) syndrome (OMIM 611943).