Table 1. Clinical biochemical testing of respiratory chain enzyme activities in the proband’s fibroblasts.

	Proband	Reference range
Complex I	119 mU/U CS	163–599 mU/U CS
Complex II	286 mU/U CS	335–888 mU/U CS
Complex III	632 mU/U CS	570–1383 mU/U CS
Complex IV	103 mU/U CS	288–954 mU/U CS
Complex V	630 mU/U CS	193–819 mU/U CS
CS	412 mU/mg	151–449 mU/mg