These are two siblings with global developmental delay, a boy 42 months old and a girl 16 months old. They were born at full term via a C-section and vaginal delivery, respectively. They both have hypotonia and autistic features, and IQ was estimated to be 35 for both. Their parents are first-degree cousins, and they have had two deceased children with a similar condition. Their shared dysmorphic features are brachydactyly and microcephaly. Brain MRI and EEG were normal. Other examinations were within normal limits.