Overview Of Acute Intermittent Porphyria
Acute intermittent porphyria is a subtype of a larger group. Porphryrias are a rare group of inherited blood disorders that occur when heme, an important component of hemoglobin, isn’t made properly. Hemoglobin is an essential protein in red blood cells that allows them to carry oxygen throughout the body. Heme can also be found in myoglobin, a protein found in certain specific muscles.
Acute intermittent porphyria in particular is characterized by sudden attacks of nervous system-related symptoms, which can last days to weeks before clearing up.
Commonly Associated With
Erythropoietic protoporphyria, Acute intermittent porphyria, Porphyria cutanea tarda, Congenital erythropoietic porphyria, and Hereditary coproporphyria
Causes Of Acute Intermittent Porphyria
Porphyria is an inherited disorder, so it often passes down through families.
Mechanism-wise, acute intermittent porphyria occurs when there is a disruption in the heme-making process. During the normal process, the body makes porphyrins during several steps. But, those with porphyria lack certain enzymes that are necessary for this process to work as expected. Because of this, they end up with abnormal build-ups of porphyrins or other chemical in their bodies.
There are quite a few different varieties of porphyria. For example, the most commonly seen form is porphyria cutanea tarda (PCT).
Infections, medications, alcohol, and hormones such as estrogen can trigger attacks in some particular types of porphyria.
Symptoms Of Acute Intermittent Porphyria
Porphyria attacks typically present with three major symptoms:
- Sensitivity to light, which can cause blistering, rashes, and scarring of the skin (called photodermatitis)
- Abdominal pain or cramping (but only for some forms of porphyria)
- Nervous system and muscle dysfunctions, such as mental disturbances, seizures, and nerve damage
Attacks of porphyria can occur suddenly and without warning. These attacks often begin with severe abdominal pain, with diarrhea/constipation and vomiting following. For some forms of porphyria, sun exposure can cause blistering, sensations of intense heat, pain, and skin redness and swelling. If blisters do result they can heal quite slowly. Further, they often result in scarring or changes to the skin’s color. The scarring resulting from these blisters can be disfiguring in some cases. Another unique symptom of these attacks is that the person’s urine may turn brown or red after an attack.
Other symptoms of acute intermittent porphyria can include:
- Muscle paralysis or weakness
- Back pain
- Muscle pain (myalgia)
- Arm or leg pain
- Numbness or tingling
- Personality changes
Attacks can be life-threatening in some cases, and can cause:
- Severe electrolyte imbalances
- Severe low blood pressure
Exams & Tests
A health care provider will perform a physical exam, which will include checking for tachycardia (the heart beating too fast) and whether or not the deep tendon reflexes (knee-jerk ones, for example) work properly.
Urine and blood tests can reveal kidney problems or other problems if they exist. Some additional tests that a doctor can perform include.
- A comprehensive metabolic panel test
- Blood gas tests
- A blood or urine test to check porphyrin levels and the levels of other chemicals linked to porphyria
- An abdominal ultrasound
Treatment Of Acute Intermittent Porphyria
Some of the medications often used to treat an acute (sudden) attack of porphyria can include:
- Propranolol to keep the patient’s heart rate steady
- Pain medication
- Intravenous hematin (given through an infusion)
- Sedatives to help the patient keep calm
Other additional treatments can include:
- Phlebotomy (removal of blood), because it reduces levels of porphyrins in the patient’s bloodstream
- Low-dose chloroquine, to reduce levels of porphyrins
- Beta-carotene supplements, because they can lessen photosensitivity
- Glucose and fluids to boost carbohydrate levels, which can help limit the production of porphyrins
Depending on the type of porphyria the patient has, their provider may instruct them to:
- Avoid direct sunlight exposure as much as possible, and use sunscreen every time they do go outside
- Avoid drugs or medications that may trigger an attack
- Eat a high-carbohydrate diet
- Avoid all alcohol consumption
- Avoid skin injury as much as possible