Algorithm for understanding and categorizing porphyrias according to clinical features

The three most common porphyrias (bold outlines) represent each of the three main categories and are distinct in their clinical features, diagnostic testing, and treatment. Other less common types of porphyria in each category should be included in the differential diagnosis. VP and HCP are in the differential diagnosis of acute neurovisceral and chronic blistering cutaneous porphyria; patients may present with either (or both) findings. Additional information about the responsible genes, enzymes, and exacerbating factors are discussed in UpToDate. Refer to UpToDate for more detailed diagnostic algorithms for each of the three main clinical categories of porphyria.