Teaching an old dog new tricks: serum troponin T as a biomarker in amyotrophic lateral sclerosis

Abstract Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressive loss of upper and lower motor neurons. Diagnosis, management and therapeutic trials are hampered by a lack of informative biomarkers. Troponins (Tn) are components of skeletal and cardiac muscles. Acute elevation of cardiac isoforms of troponin I (cTnI) and T (cTnT) in serum indicates myocardial injury. Case reports suggested that serum levels of cTnT, but not cTnI are chronically elevated in ALS and other neuromuscular disorders. Using standard clinical laboratory methodologies we studied serum troponin levels in a multicentric cross-sectional cohort of 75 ALS patients and sixty controls (DESCRIBE-ALS cohort) and in a real-world cohort of 179 consecutive patients from our ALS clinic at the University Hospital Bonn. We found that serum cTnT, is elevated in >60% of ALS patients while cTnI is always normal. Serum cTnT levels increase over time and correlate with disease severity as measured with the revised ALS FRS score. There was no correlation with the phosphorylated neurofilament heavy chain (pNfH) levels in the cerebrospinal fluid. We propose that cTnT elevations in ALS are of non-cardiac origin and may serve as a proxy of lower motor neuron or skeletal muscle involvement. They potentially help to stratify patients according to lower motoneuron involvement. Further research will determine the biological origin of the cTnT elevation and its validity as a diagnostic and/or prognostic marker. Our finding also serves as a reminder to interpret cTnT with caution elevations in patients with neuromuscular diseases.