CHIT1 serum concentration of 151 patients with NMD or primary mitochondriopathy was determined by enzyme-linked immunosorbent assay, and compared to 38 healthy controls and 8 patients with Niemann pick disease type C. Results were controlled for age, sex, CRP and CHIT1 polymorphism, and compared to several established markers (CK, FGF21, GDF15). This evidence concerns the gene FGF21 and Niemann-Pick disease type C.