TRIM37 and mulibrey nanism: Mulibrey nanism (MUscle-LIver-BRain-EYe nanism, MUL, OMIM #253250) is a rare autosomal recessive disorder caused by biallelic loss of function variants in the TRIM37 gene (tripartite motif–containing protein 37, OMIM # 605073) (1, 2).