Patients with complex I deficiency due to NUBPL mutations often present with cerebellar dysfunction (e.g., ataxia, dysarthria, nystagmus, and tremor) and brain MRIs may show cerebellar atrophy but this may not be apparent until a later age. In patients without the c.815-27T>C variant (see Molecular characteristics), hypotonia was often observed but clinical features could also include dystonia, bilateral striatal necrosis, and thalamic involvement. Biochemical assays (e.g., complex I defects or high lactate) for mitochondrial dysfunction are often negative and should not be relied upon to rule out NUBPL complex I deficiency.
NUBPL