Hereditary porphyrias comprise a group of eight metabolic disorders of the haem biosynthesis pathway, characterised by acute neurovisceral symptoms and/or skin lesions. Each porphyria is caused by abnormal functioning of a particular enzymatic step, resulting in specific accumulation of heme precursors. Seven porphyrias are due to a partial enzyme deficiency, while a gain-of-function mechanism has recently been identify in a novel porphyria. Acute porphyrias present with severe abdominal pain, nausea, constipation and confusion, and are sometimes complicated by seizures and severe neurological disorders, which may be life-threatening. Cutaneous porphyrias can also be present, with either acute painful photosensitivity or skin fragility and blisters. Rare recessive porphyrias usually manifest in early childhood with either severe chronic neurological symptoms or chronic haemolysis and severe cutaneous photosensitivity. Porphyrias are still under-diagnosed, but recent advances in the pathogenesis and genetics of human porphyrias are leading to better care of these patients and their families.