The most common and significant among the three types of porphyria. Acute episodes typically manifest between the ages of 20 and 30. Characteristically, individuals experience intense burning or cramp-like abdominal pain, vomiting, and constipation. The nervous system is also affected, leading to limb and trunk paralysis, and later, cranial nerve involvement. Psychological disturbances, rapid heart rate, elevated blood pressure, and signs of angina are not uncommon. While remissions can be dramatic at times, the long-term prognosis is generally unfavorable. Urine may appear reddish-brown or purple, either upon voiding or after standing for several hours. Certain barbiturate and sulphonamide medications are known to trigger these attacks.