Table 1.

NMDAS traits including threshold values for analysis as binary traits

Trait	Threshold score	Phenotype description	NMDAS section
Psychiatric involvement	3	Moderate to severe, warranting specialist treatment	II
Cerebellar ataxia	2	At least unable to maintain heel‐toe walking or displaying mild unilateral dysmetria	III
Migraine	5	Four days per month or more	II
Cognition	3	Combined centiles of 29 or below on Wechsler Test of Adult Reading, Symbol Search and Speed of Comprehension Test	III
Neuropathy	2	At least sensory impairment (e.g., glove and stocking sensory loss)	III
Dysphonia‐dysarthria	2	Showing at least mild impairment (clear impairment but easily understood)	III
Seizures	1	At least past history of epilepsy	II
Encephalopathy	1	At least past history of encephalopathy	II
Stroke‐like episodes	1	At least transient focal sensory symptoms	II
Visual acuity	3	Combined Snellen fraction > 6/36	III
Ptosis	2	At least unilateral ptosis obscuring 1/3 of pupil	III
CPEO	2	Abduction of at least one eye incomplete	III
Hearing impairment	3	At least moderate deafness (e.g. regularly requiring repetition), not fully corrected with hearing aid	I
Gastrointestinal disturbance	4	Dysmotility requiring admission or persistent and/or recurrent anorexia/vomiting/weight loss	II
Myopathy	2	Mild but clear proximal weakness in hip flexion and shoulder abduction and minimal weakness in elbow flexion and knee extension	III
Diabetes	2	At least impaired glucose tolerance (in absence of intercurrent illness)	II
Cardiovascular involvement	2	At least asymptomatic left ventricular hypertrophy on echo or nonsustained brady/tachyarrhythmia on ECG	II

Thresholds were defined based on the NMDAS clinical descriptors for each trait, to ensure traits were as objective as possible.