Overlapping Phenotype of Adult-Onset ALPK3-Cardiomyopathy in the Setting of Two Novel Variants

Inherited cardiomyopathies (CMPs) are fairly common causes of morbidity and mortality, particularly, in young individuals. In substantial number of cases, only morphological diagnostic criteria cannot distinguish one CMP from another because of incomplete penetrance, advanced stage of the disease, or overlapping phenotypes. Genetic testing has become a mandatory tool for definite diagnosis that is required for family screening, individual prognosis, and personalized treatment strategy in routine practice. In parallel, accumulation of genotype-phenotype correlations, especially for rare genes, promotes the deciphering of underling molecular mechanisms and the development of targeting treatment of CMPs. Here we present an adult-onset case comprised morphological features of several CMPs: asymmetric left ventricle (LV) hypertrophy, severe systolic dysfunction, LV hypertrabeculation and restrictive physiology. Using next-generation sequencing, two novel variants (NM_020778.5:c.1958C>G:p.Ser653* and c.3491G>A:p.Arg1164Gln) in alpha-protein kinase 3 (ALPK3) gene were identified and confirmed with Sanger sequencing. The trans-position (location on different alleles) of identified ALPK3 variants was established by plasmid cloning method. The ALPK3 gene, encoding nuclear alpha-protein kinase 3, has only recently been associated with CMPs and there are still few clinical data on ALPK3 variant carriers. To date, only five affected individuals with adult-onset CMPs in the setting of biallelic variants of ALPK3 gene have been reported.