For example: Huntington, minocycline, R6/2.

You can use boolean opeartors OR and AND to create your queries, e.g.:
minocycline AND R6/2
SCA3 OR SCA6 OR SCA17
(HD AND SCA3) OR BLOOD

You can also use the NOT operator:
R7E or PrP-SCA7-c92Q not nuclear inclusions
R7E or PrP-SCA7-c92Q not nuclear inclusions not retinopathy
R7E or PrP-SCA7-c92Q not (nuclear inclusions or retinopathy)
NOT anxiety
NOT SCA3 NOT SCA17 NOT anxiety