count function alternative in postgres

Is there any alternative of mysql function COUNT(DISTINCT expr,[expr...]) in
postgres. We get error if we 

write count like this count(distinct profile.id, profile.name, profile.age)
but it works well in mysql.

Reference url is given below 

http://dev.mysql.com/doc/refman/5.1/en/group-by-functions.html#function_count-distinct

Thanks
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