The c.1106C>T (p.Pro369Leu) variant in ACTA1 is a missense variant predicted to cause substitution of proline by leucine at amino acid 369. This variant is absent from gnomAD v4.1.1 (PM2_Supporting). The computational predictor REVEL gives a score of 0.922, which is above the threshold of 0.7, evidence that correlates with impact to ACTA1 function (PP3). ACTA1, in which the variant was identified, is defined by the ClinGen Congenital Myopathies VCEP as a gene that has a low rate of benign missense variation and where pathogenic missense variants are a common mechanism of disease (PP2). This variant has been reported in 4 probands with nemaline myopathy, 1 with nemaline rods (PS4_Moderate; PMIDs: 19562689, 26172852; ClinVar SCVs: SCV000589626.2, SCV002287790.1; Internal lab contributors: GeneDx, Invitae). At least one patient with this variant displayed nemaline rods and type 1 fiber predominance, which is highly specific for alpha-actinopathy (PP4_Moderate, PMID: 26172852). The variant has been reported to segregate with autosomal dominant nemaline myopathy in 3 affected family members from 1 family (PP1; ClinVar SCV: SCV000589626.2, Internal lab contributors: GeneDx). In summary, this variant meets the criteria to be classified as pathogenic for autosomal dominant alpha-actinopathy based on the ACMG/AMP criteria applied, as specified by the ClinGen Congenital Myopathies VCEP: PP4_Strong, PS4_Moderate, PM2_Supporting, PP1, PP2, PP3. (Congenital Myopathies VCEP specifications version 2; 08/27/2024)