Fig. 2

Longitudinal change in spirometry by age. Pulmonary function as assessed by spirometry [percent forced volume vital capacity (% FVC)] was impaired but largely stable for most; only 3 (12%) patients achieved normal FVC > 80%. Although there was no indication of obstructive syndrome, 15 (60%) had signs of restrictive syndrome on last evaluation with median FVC of 63% (range 38–79%). Six patients (24%) were unable to perform pulmonary function test on their last follow-up evaluation because of severe cognitive impairment. Note be taken that the youngest age for spirometry evaluation was 6 years