[Friedrich Wilhelm I and porphyria].

Historical evidence has been collected attempting to diagnose members of royal houses, perhaps most publicized by Macalpine and Hunter (1969) for George III and his assumed porphyria, claiming that his insanity was a classic case of thereof. This rare metabolic disease presents with a variety of signs and symptoms: skin disease, abdominal pain, tachycardia, and neuro-psychiatric findings. The porphyrias are hereditary and since George III and Frederick William I share ancestors it seemed reasonable to investigate if the latter may also have suffered from porphyria. The pathography of both kings is meticulous, showing for both that abdominal pain, erratic behavior, restlessness, and discolored urine were frequently observed and complete recovery interictally was common. Intercurrent illnesses, fasting, alcohol and even tobacco smoking have been shown to be inducers of attacks and these risk factors are well documented in royal history.--The diagnosis of porphyria was not recognized then and other names were used, such as Cachexia hypochondriaca, Asthma spasmodico flatulentum, dolores arthritici.--We propose that Frederick William I suffered from an inducible porphyria.