Porphyrias: where do these rare blood diseases come from?
Porphyrias: what are they exactly?
Before explaining what porphyrias are, we must take a detour to the side of the heme. Thehème is a molecule which, in the body, participates in the manufacture ofhemoglobin, a protein (found in red blood cells) essential since it allows the transport of oxygen to the various organs of the body.
The synthesis of heme is a complex process which takes place in several stages, at the level of the liver and the bone marrow: enzymes make it possible to pass from one stage to the next. The last step in this production is to conjugate a porphyrin molecule with an iron core to (finally) end up with heme.
Problem: when a step of this process is not carried out correctly (due to enzymatic dysfunction), the heme thus produced is not of good quality, which leads to hemoglobin which is not fully functional.
Porphyrias: definition. Porphyrias are a group of rare genetic diseases which correspond to a synthetic defect in heme, with an accumulation of the “materials of manufacture” of this molecule (porphyrin, but also the precursors of porphyrin: acid δ- aminolevulinic APA and porphobilinogen PGB) in the body.
There are a total of 8 porphyrias, each porphyria being the consequence of a deficit of one of the enzymes involved in the synthesis of heme:
- Hepatic porphyrias (porphyrin, APA and PGB accumulate in the liver): acute intermittent porphyria (PAI: this is the most common of the hepatic porphyrias), variegata porphyria (PV), hereditary coproporphyria (CH) and Doss porphyria (PD: it is extremely rare),
- Erythropoietic porphyrias (porphyrin and its precursors accumulate in the bone marrow): porphyria cutanea tarda (PCT), erythropoietic protoporphyria (PPE), X-linked dominant erythropoietic protoporphyria (PPEDLX) and congenital erythropoietic porphyria ( PEC).
To know. Porphyrias are rare diseases: it is estimated that in France, between 250 and 300 people suffer from it, which corresponds to a prevalence of 1 to 9 people in 100,000.
Porphyrias: what are the symptoms?
Attention ! Each porphyria has its specific symptoms, and symptoms may vary from patient to patient as well – note that porphyria can also remain asymptomatic. However, all porphyrias have more or less symptoms in common, which result from the accumulation of porphyrins and their precursors in the liver or bone marrow:
- Abdominal symptoms: intense stomach aches, nausea, vomiting, constipation … These mainly characterize hepatic porphyrias. There may be added: “port” urine (red in color), muscle weakness and / or increased heart rate (tachycardia).
- Skin symptoms: a photosensitivity with painful sensations of burning, tingling, itching … when the skin is exposed to the sun, the appearance of bullous lesions on exposed areas (hands, face …), a pallor … These rather characterize erythropoietic porphyrias.
- Neurological symptoms: depression, mood disorders, anxiety, irritability …
To know. Porphyrias develop in crises: these crises (which are therefore manifested by skin, abdominal and / or neurological symptoms) can be triggered by overwork and by taking certain antibiotic drugs.
Diagnosis and treatment: what treatment for porphyrias?
Diagnostic. The diagnosis of porphyria involves a blood test (intended to measure the blood level of porphyrin), a urine and stool sample, and a genetic examination. Indeed: porphyrias are genetic diseases that are transmitted in an autosomal dominant mode, which means that a parent carrying the responsible mutation has about 50% risk of transmitting it to his child if the other parent is non-carrier.
Treatments. There is no specific treatment for porphyrias; To date, there is no cure for porphyria. Management involves regular injections of blood-derived products (hemin) and the administration of chloroquine at low doses to reduce the cutaneous manifestations of these pathologies.
Thanks to Dr. Olivier-Jacques Bocrie-Jeantet, general practitioner for Medadom.
Rare Porphyrias Reference Center – French Porphyrias Center
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