After secretion, proBNP is cleaved to the active hormone BNP (amino acids 77–108) and the biologically inactive peptide NT-proBNP (amino acids 1–76).31, 32 Notably for AL amyloidosis, MAPK signaling mediates BNP transcription,33, 34, 35 supporting a direct connection between LC cardiotoxic effects with induced MAPK signaling and BNP levels. This evidence concerns the gene NPPB and laryngotracheoesophageal cleft.