equivalent of mysql's SET type?

I'm considering porting a MySQL database to PostgreSQL. That database uses
MySQL's SET type. Does anyone have advice about representing this type in
PostgreSQL?

MySQL DDL excerpt:
CREATE TABLE `transcript_variation` (
`transcript_variation_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`transcript_stable_id` varchar(128) NOT NULL,
...
`consequence_type`
set('ESSENTIAL_SPLICE_SITE','STOP_GAINED','STOP_LOST','COMPLEX_INDEL','SPLICE_SITE')
) ENGINE=MyISAM AUTO_INCREMENT=174923212 DEFAULT CHARSET=latin1;

I'm considering implementing this as a new type based on a bit vector, but I
wonder if anyone has a more flexible general solution.

Thanks,
Reece