TBL1XR1 and Global developmental delay: TBL1XR1 was first implicated as the genetic basis for Pierpont Syndrome, a rare disorder characterized by global developmental delay, epilepsy, feeding difficulties, and characteristic dysmorphic features including abnormal subcutaneous fat distribution with prominent plantar and digital fat pads and deep palmar and plantar grooves with “pillowing” of the palms and soles, along with microcephaly, midface hypoplasia, other facial anomalies, and short stature [10–14].