Porphyrias are inborn errors of metabolism in which specific enzyme defects exist in the heme synthesis pathway. Chester porphyria is a unique type of porphyria, with the clinical picture of acute intermittent porphyria (AIP) and the biochemical defects of both acute intermittent porphyria and variegate porphyria (VP). 
The first description of Chester porphyria is from a clinical observation made by an anesthetist, Zorka Bekerus, in Chester, England, in 1963 (hence the name Chester porphyria). The index case, Peter Dobson, was a salmon fisherman born in 1867 in Chester. [2, 3] Numerous family members had the condition, and the family coined the term Dobson's complaint to describe the mysterious illness. [4, 5]
Chester porphyria does not conform to any of the recognized types of acute porphyria (see image below).
The urine porphyrin excretory pattern varies from the pattern of acute intermittent porphyria to variegate porphyria. Chester porphyria exhibits reduction in enzymatic activity of both porphobilinogen deaminase (an enzyme with reduced activity in acute intermittent porphyria) and protoporphyrinogen oxidase (an enzyme with reduced activity in variegate porphyria). Chester porphyria manifests with attacks of neurovisceral dysfunction common to all acute porphyrias. Unlike in variegate porphyrias, cutaneous photosensitivity is not a feature of Chester porphyria.
The frequency of Chester porphyria is low, and it is only described in the city of Chester, England.
The mortality rate of Chester porphyria is high. Morbidity is significant. Many members of the Chester family were afflicted with hypertension and renal disease. Significant morbidity is associated with painful porphyric crises in patients affected with Chester porphyria. Tracing of the ancestry of the Chester family shows that 14 members had peripheral motor neuropathy; 6 of the 14 developed bulbar palsy, and 4 died as a result. [2, 3]