Typically, names ending in the letter a add an n to the end to make an adjective, while other vowels add an an.
... Amychophobia[?] Amylo-1,6-glucosidase deficiency[?] Amyloid angiopathy[?] Amyloid Neuropathies, Familial[?] Amyloid polyneuropathy, transthyretin related[?] ...