Porphyria for the general physician.

Most physicians will probably identify no more than one or two cases of porphyria during their career, but will have excluded the diagnosis in many more and thus have a high threshold for contemplating the diagnosis. It is an increasingly important diagnosis to make because prevention of attacks is essential, effective treatments are available, and family studies and medico-legal issues are of increasing relevance. The porphyrias may be currently classified as primary (genetic) or secondary, with the former subdivided into neuropsychiatric, cutaneous or mixed.1 Recent studies have clarified the biosynthetic pathway for haem and the regulatory steps involved. More importantly, analytic techniques have been improved and porphyrin precursors can now be accurately analysed using high-performance liquid chromatography, assays of the relevant enzymes are relatively straightforward and molecular genetic studies available for general use. The establishment of two supraregional assay (SAS) centres for porphyrins and the porphyrias has placed diagnostic and clinical facilities on a more professional basis. Table 1 outlines the genetic porphyrias and the clinical and diagnostic features.