© 2020 Peripartum cardiomyopathy (PPCM) is characterized by development of left ventricular systolic dysfunction and heart failure that occurs towards the end of pregnancy or in the postpartum period in the absence of structural heart disease. A complex interplay of pathophysiological mechanisms likely contributes to the PPCM phenotype. Mutations in the mitochondrial thioredoxin reductase gene (TXNRD2) have been identified as a cause of dilated cardiomyopathy. We report a case of a shared, inherited genetic mutation in the TXNRD2 gene in a mother with PPCM and her infant son who died of dilated cardiomyopathy.