TTN missense variants in two siblings with asymmetric facial and limb weakness

•Titinopathy is a kind of myopathy caused by mutations of the Titin (TTN) gene, which encodes a large protein, titin, that is expressed in cardiac and skeletal muscles.•Titinopathy patients present limb muscle weakness and atrophy, respiratory failure, cardiac failure, but rarely facial weakness.•Here we report a case of siblings having titinopathy with three TTN gene variants including two known variants and one novel variant (c.52108G > A (p.A17370T) in exon 251).•These siblings showed unique asymmetric muscle weakness in both their faces and limbs, suggesting an association between unilateral facial muscle weakness and TTN gene variants.