Defects in this process have a severe impact on human health [19,22] and, indeed, loss-of-function mutations in NFU1 and other proteins involved in [Fe‐S] cluster assembly have been described in multiple mitochondrial dysfunction syndromes (MMDS), a rare disease characterized by neurological regression, reduced motor control (dystonia) and pulmonary hypertension. The gene discussed is NFU1; the disease is pulmonary hypertension.