Table 1:

Clinicopathologic summary of HD/ALS cohorts.

Case #	Age at death (years)	Sex	CAG repeat size	Clinical details	Family history	Pathologic findings
Discovery cohort
1	57	Woman	41	ALS onset 24 months antemortem. She initially presented with reduced grip strength (left arm) that spread contralaterally. Electromyography showed scattered fasciculations 3 months before death, questionable chorea (non-specific signs- diagnostic confidence of HD: 1 indicating may be normal for age)	Paternal HD (CAG: 41)	ALS (TDP43+ aggregates) HD grade 1/4 (HTT+ aggregates)
2	58	Man	44	HD motor onset 6 years before death. Chorea, cognitive decline and behavioral changes 10 years prior to HD motor onset. ALS was not clinically diagnosed antemortem.	No known HD family history	HD grade 4/4 (HTT+ aggregates); ALS (TDP43+ aggregates)
Validation cohort
3	55	Not available	41	HD	Not available	HD, ALS
4	44	Not available	N/A	Not available		HD grade 1/4, ALS
5	61	Man	42	HD and ALS		HD grade 2/4, ALS
6	67	Woman	N/A	Not available		HD grade 3/4, ALS