SIL1 and Marinesco-Sjogren syndrome: In fact, immunofluorescence analysis of the muscle biopsy from P8 (p.(Phe217Leu); p,(Asp236His) and P9 (p.(Tyr478Cys); missing) showed normal α-dystroglycan glycoepitope staining (data not shown). The other highly relevant differential diagnosis with a reminiscent clinical spectrum is Marinesco-Sjogren syndrome (MSS) caused by bi-allelic mutations in SIL1. MSS is characterized by intellectual disability, early onset cataracts, ataxia with cerebellar atrophy and myopathy.