In Arthur Conan Doyle’s “The Adventure of the Dying Detective,” what illness does Holmes pretend to have?

In Arthur Conan Doyle’s “The Adventure of the Dying Detective,” Holmes pretends to have a fatal tropical disease.

Holmes tells Watson that he has contracted a rare illness associated with travel in tropical regions. He refuses Watson’s ordinary medical assistance and insists that only the specialist Culverton Smith can help him. Watson is deeply alarmed because Holmes appears dangerously ill.

The performance is an investigative trap. Holmes wants Smith to believe that the disease has affected him, hoping Smith will reveal his responsibility for poisoning another man. Watson follows Holmes’s instructions and helps bring the necessary witness and police assistance into position.

The story first appeared in 1913. Its exact disease is not presented as a normal diagnosis Holmes genuinely suffers from; the important fact is that the illness is fabricated as part of his plan. That distinction prevents confusion with a real medical case.