Novel combination of FLNC (c.5707G>A; p. Glu1903Lys) and BAG3 (c.610G>A; p.Gly204Arg) genetic variant expressing restrictive cardiomyopathy phenotype in an adolescent girl.

Pediatric restrictive cardiomyopathy (RCM) is the rarest in its group and accounts for only 2.5-5% of all the diagnosed cardiomyopathies in children. It is a relentless disease with poor prognosis, and heart transplantation is the only long-term treatment option. The aetiology of pediatric RCM varies and includes conditions such as endomyocardial fibrosis, storage disorder (Fabry's disease, MPS), drugs, radiation, post-cardiac transplantation and genetic. Genetic causes encompasses mutations in sarcomeric (troponin I and T, actin, myosin and titin) and nonsarcomeric protein-coding genes (Desmin, RSK2, lamin A/C and bcl-2-associated athanogene 3 ( BAG3 )). Inheritance of RCM could be autosomal dominant, autosomal recessive and X-linked. Here, we report a case of RCM in an adolescent girl, who was symptomatic with palpitations and breathlessness on exertion. The patient showed presence of rare variants in FLNC (c.5707G>A; p.Glu1903Lys) and BAG3 genes (c.610G>A; p.Gly204Arg). These two variants were detected individually in asymptomatic father and mother, respectively. FLNC gene codes for gamma filamin. These filamin proteins play important role in maintaining the structural integrity of the sarcomere. BAG3 is the main component of the chaperone-assisted selective autophagy (CASA) pathway. Mutant FLNC leads to the formation of protein aggregates which are cleared by an active protein quality control system including CASA pathway. For further verification, in silico protein-protein interaction was performed using online software and tools. The results showed evident interaction between FLNC and BAG3 with significant binding score (-826.6) between them.