Porphyrins Blood Test

Definitions

Porphyrins are pigments which occur in plants and animals. They belong to a chemical group which helps to form several vital substances in the body like hemoglobin, which is the protein, found in red blood cells which are responsible for carrying oxygen in the blood.

The three types of porphyrins that are related to blood cells are protoporphyrin, Coproporphyrin and uroporphyrin. These three substances can be measured in the blood. Protoporphyrin, forms the maximum amount, so the porphyrins blood test is also called the PROTO test. There are other tests to detect the levels of particular porphyrins.

The test usually takes a measurement of the total level of porphyrin in the body. The reference value is the level of porphyrins which are found in a healthy person. The normal range of the three porphyrins in a healthy person is as follows:

Total levels of porphyrin : 16 mcg/dL to 60 mcg/dL

Coproporphyrin : less than 2 mcg/dL

Protoporphyrin : 16 to 60 mcg/dL

Uroporphyrin levels : less than 2 mcg/dL

NB: mcg/dL means micrograms per deciliter

Why the Test is Performed?

Usually the purpose of this test is for diagnosis of porphyrin disorders in connection with red blood cells, popularly known as porphyria. Porphyria is not just one disease but a combination of up to eight disorders and each disorder being different from the other. The only common factor in all these diseases is that they are characterized with an excessive production of “porphyrins”, also known as “porphyrin precursors”. As mentioned earlier, the symptoms of each condition is different, therefore the treatment will also vary in the same way. This is why it is difficult to make generalizations regarding these types of disorders.

The symptoms mostly manifest themselves in the skin or the nervous system. The more extreme forms of porphyria occur in the nervous system.

Causes of Porphyria

The causes are as different in the different deficiency of enzymes. These enzymes are used for the production of a substance called “heme” in the body. Heme is vital to several body functions and is present in large quantities in red blood cells and bone marrow, but is also present in other areas of the human body like the liver. These enzyme deficiencies are usually hereditary. External influences like drug consumption, exposure to sunlight, diet and chemicals can have a direct relationship to the symptoms.

Hereditary Factors

Porphyrins which are inherited can be inherited from one parent (autosomal) or both parents (autosomal recessive). People with autosomal porphyria will have one normal and one abnormal gene. On an average, half of their offspring will inherit the disease gene. The other half will be normal. If a person has autosomal recessive porphyria, each of their offspring will have the abnormal gene from the abnormal parent which will be coupled with the normal gene from the normal parent. If both parents have the gene, then about ¼ of their children will have both the abnormal genes and they will definitely develop the symptoms of the disorder. As porphyrias are rare, it is not likely that over one type could occur in a single family.

Sunlight and Porphyria

Except in a couple of types, all other forms of porhyria exhibit sensitivity to sunlight. The extent to which the patient is sensitive to sunlight may vary depending on the type of porphyria that a person has. The ultraviolet light of sunlight reacts with porphyrin and damages the skin tissue. Some patients have enough tolerance to sunlight without the porphyrin levels being reduced. However, in other cases treatment to lower the porphyrin levels may be required, and then the patient can tolerate sunlight.

Along with other tests, it is used for diagnosis of neurological and skin disorders and even lead poisoning.

The above tests are conducted when these general abnormalities occur. The specific conditions under three categories may be as follows:

  • Increase in the Level of Coproporphyrin: This can lead to a development of Sideroblastic anemia which occurs due to overproduction of ringed sideroblasts. It could be caused genetically or a part of a condition known as “myelodysplastic syndrome”
  • Increase in the Level of Protoporphyrin: This can be due to general infection or it can also indicate sideroblastic anemia or Thalassemia. It can also be an indication of lead poisoning or iron deficiency.
  • Increase in the Level of Uroporphyrin: This can be caused due to congenital erythropoietic porphyria (CEP). This very rare disease is also called Gunther’s disease. The actual enzyme which is deficient is uroporphyrinogen III cosynthase or uroporphyrinogen III synthase. Variations of the gene for this enzyme are known to have occurred in different families. The symptoms for this disease manifest themselves at an early age, sometimes even at the fetal stage. Less commonly, they show up during adulthood.

Thus, it is observed that porphyrins blood test is a test which should be done with several variations to be taken into consideration. Depending on the symptoms exhibited by the patients, the particular type of blood test is done. What is important in all cases of porphyria is proper identification of the type of porhphyria, to understand the correct blood test to be conducted.