When the GAPDH reference gene was used for normalisation, the geometric mean expression levels for HERV-K gag and HERV-K pol were very slightly higher in the ALS patients than in the control group but the converse was true for HERV-K env. None of these marginal differences in HERV-K expression levels approached statistical significance. Here, GAPDH is linked to amyotrophic lateral sclerosis.