Hereditary coproporphyria (HCP) is a rare inherited form of liver (hepatic) porphyria, characterized by neurological symptoms in the form of episodes (acute attacks) of stomach pain, nausea, vomiting, weakness, numbness, and pain in the hands and feet (neuropathy). The porphyrias are a group of blood conditions caused by a lack of an enzyme in the body that makes heme, an important molecule that carries oxygen throughout the body and is vital for all of the body's organs. Symptoms present during the attacks may include body pain, nausea and vomiting, increased heart rate (tachycardia), and high blood pressure. Less common symptoms include seizures, skin lesions, and paralysis of the arms and legs, body trunk, and respiratory muscles. Most individuals with HCP do not have any signs or symptoms between attacks. HCP is caused by genetic changes in the CPOX gene and is inherited in an autosomal dominant manner. Diagnosis is based on the symptoms and specific blood, urine and stool testing.