What's the adjective of this word? What's the agentive noun? "This man is a dyscalculiac"? "He's dyscalculic"? Or do we have to say: "He suffers from dyscalculia"?

Thanks.

Hm. Unless there's a bad smell in here, I guess no one is sure.

Without the benefit of an informed opinion, my best shot is probably to look at words which have "calculare" as a root, and see what their adjectival endings are.

The adjective of "calculate" is "calculative"; so, shouldn't the adjective of "dyscalculia" be "dyscalculative" ?

What do you think?

That sounds like a valid analogy save for 'calculative' not being an involuntary condition. Following 'anemic' and 'dyslexic' as a pattern would make it 'dyscalculic' as in your first post.