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 usually begin around 20-30 years of age, but have been reported at younger ages. Signs and 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 mutations 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. Treatment is based on preventing the symptoms. An acute attack requires hospitalization, medications, and treatment with heme therapy.

Heme is a red pigment composed of iron linked to a chemical called protoporphyrin. Heme has important functions in the body. The largest amounts of heme are in the form of hemoglobin, found in red blood cells and bone marrow. Hemoglobin carries oxygen from the lungs to all parts of the body. In the liver, heme is a component of proteins that break down hormones, medications, and other chemicals and keep liver cells functioning normally. Heme is an important part of nearly every cell in the body.

The symptoms of hereditary coproporphyria (HCP) may be different from person to person. Some people may be more severely affected than others and not everyone with hereditary coproporphyria will have the same symptoms. Many individuals with a CPOX genemutation do not experience any symptoms of HCP.

In people with HCP, additional factors; such as hormonal changes, certain drugs, excess alcohol consumption, infections, and fasting or dietary changes; may trigger the appearance of symptoms. Symptoms appear as acute attacks or episodes that develop over a period of days. The timing and severity of attacks vary from one person to another.

The symptoms of an acute attack include:

• Severe stomach pain leading to nausea and vomiting
  • back and leg pain
• High blood pressure
• Rapid heartbeat (tachycardia)
• Seizures (less common)
• Weakness, numbness in the arms and legs (peripheral neuropathy)
• Skin findings (in about 20% of people with HCP)
  • extreme sensitivity to sunlight (photosensitivity)
  • fragile skin

In between attacks, people with HCP are often symptom-free.

Hereditary coproporphyria (HCP) is caused by a genetic change (mutation in the CPOX gene. However, having a CPOX gene mutation alone does not cause symptoms. Additional factors (such as hormonal changes, specific drugs, excess alcohol, fasting) are needed to trigger an attack and the appearance of symptoms. Some people with CPOX gene mutations never have symptoms of HCP.

Hereditary coproporphyria (HCP) is inherited in an autosomal dominant pattern. All individuals inherit two copies of each gene. In autosomal dominant conditions, having a mutation in just one copy of the CPOX gene causes the person to have HCP. The mutation can be inherited from either parent. Some people are born with hereditary coproporphyria due to a new genetic mutation (de novo) and do not have a history of this condition in their family. There is nothing either parent can do, before or during pregnancy, to cause a child to have this.

Each child of an individual with an autosomal dominant condition has a 50% or 1 in 2 chance of inheriting the mutation and the condition. Offspring who inherit the mutation may develop HCP, although they could be more or less severely affected than their parent. Sometimes a person may have a CPOX gene mutation for HCP and show no signs or symptoms of it.