Isolated cardiac sarcoidosis associated with the expression of a splice variant coding for a truncated BTNL2 protein.

A 33-year-old woman presented with clinical signs of heart failure and previously diagnosed complete atrioventricular block. DNA sequencing revealed a homozygous point mutation in exon 5 of the btnl2 gene coding for a truncated protein which lacks the membrane-anchoring motif. This single nucleotide polymorphism is known to be a risk factor for sarcoidosis. Indeed, endomyocardial biopsy demonstrated multiple nonnecrotizing granulomas composed of epitheloid cells and moderate numbers of multinucleated giant cells. Because no other organs were affected, isolated cardiac sarcoidosis was diagnosed and treated with corticosteroids. Thus, detection of the disease-associated btln2 allele may help to identify patients with sarcoidosis as the underlying cause of heart failure.