Nausea may be accompanied by vomiting. Fever, convulsions, and respiratory paralysis are less common. Acute attacks generally have a brisk onset of hours to days, but characterization of a typical prodrome is impossible. An attack may last several days to several weeks. An acute attack is often precipitated by some event or drug exposure.
Drugs associated with attacks include ethanol, barbiturates, and anticonvulsants.
An attack may be precipitated by dietary restriction. Episodes are influenced by hormonal status, with the disease typically becoming manifest after puberty. Acute attacks are more common in women, may occur in association with menses, and may cease with menopause. The neurologic and psychiatric symptoms are essentially identical. It is difficult to diagnosis an acute porphyria between attacks for a variety of reasons.