Increased aminotransferases do not necessarily mean hepatotoxicity of CFTR modulator therapy.

Aim of the study: The presence of macroenzymes may mimic treatment related hepatotoxicity.

Material and methods: We present a female subject who developed high alanine aminotransferase (ALT)/aspartate aminotransferase (AST) activity during cystic fibrosis transmembrane regulator (CFTR) modulator therapy.

Results: The differential work-up did not show any underlying liver disease. CFTR modulators were stopped with subsequent normalization and immediate rise of ALT/AST after modulators were restarted, which was interpreted as the presentation of CFTR modulator hepatotoxicity. Before permanent CFTR modulators' discontinuation the patient's blood was tested for the presence of macroALT/macroAST and the result was positive. The patient is continuing a CFTR modulator treatment that is being supervised using standard laboratory tests and a test detecting the presence of macroenzymes. At three subsequent measurements the tests showed the presence of macroenzymes.

Conclusions: Our patient shows that increased ALT/AST during CFTR modulator therapy may be related to the induction of macroenzymes and not necessarily to hepatotoxicity. Patients with high ALT/AST activity should be considered for testing for the presence of macroenzymes.