HSPD1 and Intellectual disability: Two siblings, a younger brother with hypomyelinating leukodystrophy and an elder brother with severe intellectual disability and autistic features, had independent de novo variants of <i>HSPD1</i> c.139T > G (p.Leu47Val) and <i>HIP1</i> c.1393G > A (p.Glu465Lys), respectively.