Of serum Mi-2β positive ILD, one patient (IPF) demonstrated Mi-2β reactivity on a positive level in BALf, one patient (HP) on a weakly positive level and three (n = 2 HP and n = 1; RA-ILD) on a borderline weakly positive level (intensity level 6–10). Here, CHD4 is linked to idiopathic pulmonary fibrosis.