Alternatively, the heterogeneity in MC1 may indicate subtypes of MC1 documenting different histories of the MC lesion (e.g. initial vs. recurrent) or reflecting different aetiologies, i.e. autoinflammation against disc material vs. subclinical infection of the disc with Cutibacterium acnes [8,[28], [29], [30], [31], [32]]. This evidence concerns the gene ATP7A and infection.