Porphyria – enzyme defect with consequences

Porphyria – enzyme defect with consequences

Porphyria is a group of rare metabolic disorders with a wide range of manifestations. Porphyria can be acute or chronic, cause minor or life-threatening symptoms, and affect a wide variety of organs. The diagnosis is, therefore, often challenging to make. Learn more about the causes, symptoms, diagnosis, and treatment of porphyria here.

How does porphyria develop?

As different as the forms are, they have one thing in common: the formation of porphyrins is always disturbed. Porphyrins are chemical compounds, mostly with metals. They are responsible for the colour of proteins, such as the green chlorophyll in plants and the red colour of blood cells and muscles.

Porphyrins are an essential component in human and animal organisms; they are broken down in the liver via intermediate stages, giving the bile a greenish colour. Various enzymes are involved in this incorporation, conversion and degradation, especially in the bone marrow and liver. This process is disrupted if one or more need to be included or fixed. Such an enzyme defect can be inherited or acquired (for example, after lead poisoning).

 

What forms are there?

There is not just one classification, but several, which are made according to different criteria. A distinction is made according to origin (congenital – acquired), site of enzyme formation (bone marrow – liver), and course (acute – chronic). Depending on where the affected enzymes are mainly formed, the

  • erythropoietic form  (disorder in the blood-forming bone marrow) and
  • hepatic form  (disorder in the liver cells) as well
  • a combination of these two (erythrohepatic form).

For example, if the incorporation into blood cells or muscle protein is disrupted, the concentration of porphyrins and their precursors in the blood increases; the specialist then speaks of porphyrinemia. If the conversion is disturbed, these are more likely to be deposited in the skin and other tissues and damage them. The concentration in the urine (porphyrinuria) or stool can also be increased.

How is the disease manifested?

Symptoms depend on which enzyme is affected. The division into forms with a sudden onset ( porphyria acute) and a chronic course ( porphyria chronica ) has proven effective, as they are associated with typical symptoms.

In acute forms, abdominal pain, cardiovascular problems, neurological disorders and psychological problems such as depression occur. Chronic porphyrias, on the other hand, are characterized by changes in the skin when exposed to light.

 

Two critical forms at a glance

By far, the most common is the

  • Porphyria cutanea tarda (PCT) is a chronic form likely to be inherited or acquired. A typical feature is the formation of blisters on skin exposed to light, for example, the back of the hand or the neck. There is increased pigmentation and hair growth. Liver damage often occurs as well. Excreted urine darkens to pink or brown under the influence of light.
  • Intermittent acute porphyria (AIP) is a hereditary, life-threatening form. It usually first appears in early adulthood. Certain factors, such as infections and medication, but also stress, alcohol and hunger, can trigger an acute attack. The symptoms are varied. The spectrum ranges from abdominal colic with nausea and vomiting to fevercardiac arrhythmias, and increased blood pressure to psychological and neurological changes such as paralysis, sensory disturbances, seizures and impaired consciousness. Respiratory paralysis can even occur. Therefore, in an acute attack, the person affected must be cared for in an intensive care unit. In this form, too, the urine darkens.

How is the diagnosis made?

First, the medical history and the symptoms with the mixture of symptoms are decisive. Definitive diagnosis and differentiation of form is made by determining porphyrins and their precursors in blood, urine and stool. Genetic tests are also possibly carried out.

What therapy is there?

With all forms, the most important thing is to avoid the triggers. Light protection ointments can be applied to support PCT. By taking the malaria drug chloroquine, an attempt can be made to release the porphyrins from the tissue. However, this treatment is temporary. Bloodletting is also used. In the case of AIP, the symptoms are treated in intensive care during an acute attack.

The course depends on the form and whether the triggers should be avoided. A cure has not yet been possible for any porphyria.

 

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