Tiered Classification Methology - Curated genotype and phenotype data is presented with a tiered classification of genes based on the number of de novo pathogenic loss-of-function (pLOF) variants. These variants are defined as LOF nonsense, splice site, and frameshift sequence variants and single gene deletions that include one or more exons. Candidate genes have been ranked into four tiers based on the strength of evidence, as outlined below. Genes with autosomal recessive inheritance have been placed in a separate category outside of the tiered ranking system.