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. Second, concentrations of PBG typically normalize between attacks.
Enzyme concentrations can, in theory, identify individuals at risk.
For example, in individuals predisposed to acute intermittent porphyria, the enzyme PBG deaminase is typically half the levels seen in normal individuals. Many technical difficulties limit the practical usefulness of such enzyme assays, however, and gene- based assays will probably prove to be more reliable. Gene-based testing is currently available for acute intermittent porphyria, but not for the other acute porphyrias. Bile and feces may also be used, although bile specimens are difficult to collect and fecal porphyrins suffer from extensive bacterial degradation. PCT typically presents with bullous vesicles on sun-exposed skin, although the association with sun exposure often is not recognized.