Novel USP9X variant associated with syndromic intellectual disability in a female: A case study and review.

Heterozygous variants in USP9X are associated with female-restricted X-linked mental retardation (MRXS99F), a rare syndrome characterized by neurodevelopmental delay, intellectual disability (ID), and a wide variety of additional congenital anomalies. Here, we report a girl harboring a novel de novo loss-of-function variant in USP9X (c.4091delinsAG, p.