We Body Moisturizer report a female patient with asymptomatic cor triatriatum sinister, associated with 4q34.3 deletion.Her child, carrying the same imbalance, suffers from tetralogy of Fallot.To the best of our knowledge, this is the first reported case of cor triatriatum associated with deletion of the long arm of the chromosome 4; furthermore, the majority of patients with chromosome 4 long arm syndrome have de novo Toys deletions and only few familial cases have been reported so far.