CHIT1 and chitotriosidase deficiency: In our study, apart from a single newly-diagnosed cystinotic patient homozygous for the chitotriosidase deficiency mutation, there was no overlap in chitotriosidase values between the other twelve newly-diagnosed (8 in the study group and 4 naïve patients) and age-matched controls (39 in the study group and 9 naïve patients).