How can I help a patient with severe recurrent aphthous ulceration?

Case scenario

Recently, a young man presented with a history of severe recurrent aphthous ulceration occurring over the last two or three years. When I saw him, large typical aphthous ulcers were visible on all surfaces of the buccal mucosa. He was unable to eat and had some difficulty with fluids. He had tried all of the usual over-the-counter preparations, and I was at a bit of a loss about what to advise. Should he be investigated further and what treatments can help in this situation?