Medical Moment Q&A-
Almost all cells in the body contain heme proteins. Heme proteins, such as hemoglobin, are valuable for transporting oxygen and carbon dioxide throughout the body. Other heme proteins are also important for breaking down drugs, toxins, and other harmful substances.
The process of producing heme in the cells is called porphyrin synthesis. The porphyrin synthesis process requires eight enzymes to produce heme. If there is a defect in any one of these enzymes, less heme is produced and an excess in certain types of proteins occurs which can be toxic to nerves or skin resulting in nerve damage, abdominal pain or skin blistering. The group of genetic diseases associated with defects in the enzymes that produce heme is called Porphyria. There are eight different types of porphyria:
Acute Intermittent Porphyria (AIP) - is a chromosomal dominant inherited gene defect in heme production. Most patients have no symptoms, but if symptoms are present, they can be very debilitating. The most common symptom is vague, crampy abdominal pain that can last over several hours, days or weeks. Associated symptoms include vomiting and constipation. Sometimes the pain can occur in the chest, back or extremities. Severe attacks may lead to loss of movement of an extremity. Attacks are most common in young adult women typically occurring between puberty to menopause. Diagnosis is made by a urine test during an acute attack identifying, an elevated porphyrin protein, porphobilinogen (PBG).
Variegate Porphyria (VP) - is a chromosomal dominant inherited gene defect in heme production that is common that has symptoms like AIP but can also have blistering skin lesions when someone has sun exposure. Diagnosis is made by an elevated urinary PBG during an acute attack. Further testing is needed to identify elevated total urinary and plasma porphyrins to confirm the diagnosis of VP.
Hereditary Coproporphyria (HCP) - is a chromosome dominant inherited gene defect in heme production with symptoms similar to variegate porphyria, including abdominal pain and blistering skin lesions. Diagnosis is made by an elevated urinary PBG during an acute attack. Further testing is needed to identify elevated total urinary, plasma and stool porphyrins to determine the diagnosis of HCP.ALAD Deficiency Porphyria - is a rare chromosomal recessive inherited gene defect in heme production with only a few cases reported world-wide. The symptoms are similar to acute intermittent porphyria. Diagnosis is made during an acute attack by an elevated urinary coproporphyrin and 5-aminolevulinic acid (ALA), rather than PBG.
Porphyria Cutanea Tarda (PCT) - is the most common type of the porphyrias. For some the disease can be acquired over time but for others it can be a chromosomal dominant inherited gene defect in heme production. Environmental factors including alcohol, hepatitis C, smoking, HIV, elevated iron serum levels, and estrogens can trigger the disease. Symptoms include blistering on sun-exposed areas of the skin, usually the hands and face. In addition, the skin can tear easily with mild trauma. Patients are at risk of developing cirrhosis and even liver cancer. Diagnosis is made by elevated plasma and urinary porphyrins.
Erythropoietic Protoporphyria (EPP) - is a chromosomal recessive inherited gene defect in heme production with symptoms that usually occurs in early childhood. Symptoms can include pain, burning, itching, swelling and redness that develops soon after sunlight exposure. Generally, there is no blistering. Other symptoms include iron deficiency and complications from liver disease. Diagnosis is made by elevated plasma porphyrins and red blood cell protoporphyrins.
X-Linked Protoporphyria (XLP) - is a chromosomal X-linked dominant inherited gene defect in heme production. Symptoms are similar to patients with EPP. Diagnosis is made by elevated plasma porphyrins and red blood cell protoporphyrins. Genetic testing is needed to confirm the diagnosis of XLP versus EPP.
Congenital Erythropoietic Porphyria (CEP) - is a chromosomal inherited gene defect in heme production with symptoms that can occur shortly after birth. Symptoms can be severe and include skin photosensitivity with blistering, scarring, and infections. Diagnosis is made by elevated total plasma and urinary porphyrins.