What is Porphyria?

Porphyria is a group of genetic (hereditary) disorders that originates from the rise of natural chemicals known to produce porphyrin in the body. It is a defect in an enzyme known as porphyrin, which is described as the enzyme involved in the synthesis of heme that leads to the inception of porphyria. Porphyrin is an important enzyme for hemoglobin function.   Picture Courtesy: Medindia

What are the types and classifications of porphyria?

Porphyria is an inherited disorder; in which there was a transfer of an abnormal gene from one parent to the child. Various types of the disorder follow a dominant route. They include:

• Hereditary coproporphyria 
• Acute intermittent porphyria
• Acute hepatic porphyria
• Variegate porphyria
• Porphyria cutanea tarda
• X linked protoporphyria
• Erythropoietic protoporphyria

Others that align with the recessive route include:

• Aminolevulinic acid dehydratase deficiency porphyria
• Congenital erythropoietic porphyria
• Hepato erythropoietic porphyria

In classifying porphyria, it is grouped according to the accumulating pathway (i.e., hepatic or erythropoietic or clinically; acute or cutaneous).  In the “acute” class, porphyria affects the nerves, and in “cutaneous,” it affects the skin due to sensitivity to sunlight. Therefore, acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria fall under acute porphyria. In contrast, congenital erythropoietic porphyria, erythropoietic porphyria, hepatoerythropoietic porphyria, porphyria cutanea tarda, and X linked protoporphyria are included in cutaneous porphyria. Specific porphyria syndromes include:

• Acute intermittent porphyria
• Erythropoietic protoporphyria
• Hepato erythropoietic porphyria

Genetically, it is obtained from one parent transferring a defective gene to offspring or transferring an abnormal gene from both parents. Porphyria cutanea tarda is acquired through the inheritance of the enzyme deficiency. 

How common is porphyria?

It is a rare genetic disorder. Studies have suggested that all types of porphyria combined effects fewer than 2,00,000 people in the USA [1]. The most common type of the disorder overall is porphyria cutena-tarda, which affects about 5 to 10 out of every 1,00,000 people [2]. The most common type of porphyria in children is erythropoietic protoporphyria. What are the Complications of Porphyria? The complications also depend on the form of the disorder.

• In acute porphyrias, there is a need for urgent attention during an attack. If not, it could lead to loss of life. There may be seizures, difficulty breathing, and other factors that require the patient to be hospitalized and treated.
• In cutaneous porphyrias, it can permanently damage the skin. Also, there could be an infection of blisters and abnormal skin coloration in the recovery of skin with scars. 

Diagnosis 

It is quite difficult to diagnose porphyria because of its similar symptoms to others.  On visiting the hospital for diagnosis, the doctor records the patient’s medical and family history and then performs a physical examination looking for symptoms that hint at porphyria. The combination of the symptoms below can be the criteria for an emerging attack.

• Muscle weakness
• Psychiatric symptoms
• Abdominal pain
• Hyponatremia

The red flag that indicates porphyria often is long-term abdominal pain. Other laboratory tests are also mandatory to figure out the condition. They include:

• Urine test; a single portion of urine is collected to test for an increase in porphobilinogen during the attack. An increased porphobilinogen in the urine shows a high percentage of acute intermittent porphyria, variegate porphyria, and coproporphyria.
• Blood test; the plasma level measurement is taken using fluorescence emission spectroscopy to ascertain cutaneous porphyria. 
• Stool test; to measure coproporphyria and protoporphyria 
• Erythrocyte uroporphyrinogen decarboxylase – is considered a diagnostic test for porphyria cutanea tarda [3].
• Electrolyte test
• Genetic test; to check for the enzyme defect.

Treatment

Porphyria has no permanent cure, but treatments aid in managing the risen symptoms. Acute porphyria treatment involves:

• Injecting hemin to reduce porphyrin product
• Oral administration of sugar to curtail carbohydrate
• The patient is hospitalized for treatment such as vomiting, abdominal pain, and breathing difficulties.

Cutaneous porphyria treatment involves:

• Intake of dietary supplement of vitamin D to cover for the periods of not being exposed to sunlight
• Taking malaria drugs to get rid of porphyrins earlier than usual.
• Phlebotomy, i.e., drawing out blood to reduce iron, reduces porphyrins.

 During the treatment process, the patient has to avoid the following:

• Taking alcohol 
• Avoid using medication that will initiate the acute attack 
• Fasting 
• Smoking
• Treating infection and illness promptly 
• Exposure to sunlight 
• Emotional stress 

Prevention

If genetically inherited, the patient has to avoid its triggers since it is inheritable. The doctor should enlighten the patient on the form of porphyria they are suffering from, the drugs, and inheritance.  Mortality & Survival Rate Research has shown that the mortality rate was very high in the initial porphyric attack. Compared to the years afterward when hemin therapy began, the survival rate improved.  Also, porphyria cutanea tarda can be associated with a higher mortality rate with incidences involving gastrointestinal disease and cancer of the gut, liver, and lungs.   Picture Courtesy: healthmatters

Symptoms

SIGNS AND SYMPTOMS

The symptoms are dependent on the severity. Some persons inherit it but do not show any signs of symptoms, rather, they have what is called “latent porphyria”. This is largely for those with abnormal genes.

For acute porphyria the symptoms are:

• Severe abdominal pain
• Chest, leg, and back pain
• Vomiting
• High blood pressure
• Breathing difficulties
• Diarrhea and constipation
• Brown urine 
• Muscle pain usually associated with weakness
• Seizure.

For cutaneous porphyria the symptoms are:

• Itching
• Burning pain sensation due to sunlight
• Blisters on exposure to light especially around hands, arms, and face.
• Skin redness and swellings are usually sudden and painful.

Causes

Picture Courtesy: iclinicq

Porphyria occurs as a result of a defect in heme production. Heme is a protein that carries oxygen from the lungs to all body parts, involving various enzymes. Where a specific enzyme is deficient, it accumulates porphyrin, which aids in heme making. In porphyria, the mode of inheritance varies according to the type of porphyria. Few are autosomal dominant, where only one abnormal gene is sufficient to cause the disease. Few are autosomal recessive, where the defective genes should be present on both the chromosome pairs to cause the disease. In a few more cases, the defective gene is present on the X-chromosome [4].

Other causes- environmental factors play a significant role in causing porphyria. Smoking, alcohol consumption, stress, hormonal imbalance, chronic illness, and excessive dieting may trigger porphyria.
What are the risk factors for porphyria?

FAQ

Is it advisable to use special sunscreen?

Patients with cutaneous porphyria should limit their exposure to sunlight to its barest minimum. Using transparent sunscreen will be of no help. Same thing as sunscreen with vitamin A and carotene. What helps is making use of physical sunscreen like zinc oxide. 

What is latent porphyria?

Patients with the disease who do not show symptoms have latent acute porphyria. Not that they will never have any symptoms, though, it involves other factors apart from genetic factors. On exposure to medications and certain environments, the mutation for porphyria symptoms will be altered. That is more reason for individuals with porphyria to get tested for symptoms to know about prevention and management.

How often should one check urine samples for PBG?

It is advisable to check PBG levels once a year.

Is porphyria contagious?

Not all types of porphyria are contagious, although a risk factor of developing porphyria cutanea tarda is infection with hepatitis c virus.

References

1. Ramanujam VS, Anderson KE. Porphyria diagnostics—part 1: a brief overview of the porphyrias. Current Protocols in Human Genetics. 2015;86:17.20.1–17.20.26. doi: 10.1002/0471142905.hg1720s86Bissell DM, Anderson KE, Bonkovsky HL. Porphyria. New England Journal of Medicine. 2017;377(9):862–872. doi: 10.1056/NEJMra1608634
2. https://emedicine.medscape.com/article/1389981-overview#a6
3. https://www.medindia.net/patients/patientinfo/porphyria.htm#what-are-the-causes-of-porphyria