The Thackery T. Lambshead Pocket Guide to Eccentric & Discredited Diseases (2003) is an anthology of fantasy medical conditions edited by Jeff VanderMeer and Mark Roberts, and published by Night Shade Books.
It contains generally humorous entries (in varying degrees of darkness) with describing fantastical diseases, which together detail the "secret medical history" of the 20th century.
Each entry presents a history of the disease, its characteristic symptoms, and any cure that might exist, all written in a faux encyclopedic style.
The book also includes essays about the adventures of the titular Thackery T. Lambshead, "a sort of medical Indiana Jones.
[1] A sequel anthology was released in 2011 called The Thackery T. Lambshead Cabinet of Curiosities, which was co-edited by Jeff and Ann VanderMeer.