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The neurological manifestations of porphyria: a review
Insights
Hereditary hepatic porphyrias like AIP involve excess porphyrins and precursors, causing neurological attacks. New therapies targeting enzyme activity show promise for managing acute episodes.
Area of Science:
- Biochemistry
- Neuroscience
- Genetics
Background:
- Hereditary hepatic porphyrias (PV, AIP, HC) are characterized by elevated porphyrins and precursors (ALA, PBG).
- Clinical presentation includes acute neurological episodes.
- Biochemical basis involves partial enzyme blocks in heme biosynthesis, leading to suppressed ALA-synthetase.
Purpose of the Study:
- To investigate the underlying mechanisms of neurological manifestations in hepatic porphyrias.
- To explore the role of porphyrin precursors in neurological dysfunction.
- To review current therapeutic strategies for acute attacks.
Main Methods:
- Biochemical analysis of porphyrin and precursor excretion.
- Review of clinical data on neurological involvement.
- Examination of heme biosynthesis pathway enzyme activity.
- Investigation of porphyrin precursor interactions with the nervous system (e.g., GABA receptor).
Main Results:
- Increased excretion of porphyrins and precursors (ALA, PBG) is a hallmark.
- Neurological symptoms may stem from reduced heme-proteins or toxic effects of ALA/PBG.
- Porphyrin precursors exhibit potent pharmacological effects on the nervous system, potentially involving GABA receptors.
Conclusions:
- Therapeutic strategies focusing on suppressing ALA-synthetase activity have shown success.
- Reduced ALA and PBG production is a key treatment goal.
- These therapies offer promising future treatment options for acute porphyria attacks.
Abstract:
The hereditary hepatic porphyrias, PV, AIP and HC, are characterized biochemically by increased excretion of porphyrins and the porphyrin precursors ALA and PBG. They are characterized clinically by episodes of acute neurological involvement. The increased production of porphyrins and porphyrin precursors has been shown to be due to partial enzyme blocks along the heme biosynthetic pathway which results in secondary depression of the key enzyme ALA-synthetase. The neurological manifestations could therefore be related to either a decrease in essential heme-proteins or other heme-containing compounds within the nervous system, or to a toxic effect of the over-production of the porphyrin precursors ALA and PBG. There is evidence for and against both theories. Recent work from a number of research groups has shown the porphyrin precursors to have potent pharmacological effects on the nervous system, and these are possibly related to the GABA receptor and binding site-porphyrin precursor interactions. Current studies on therapy of the acute attack have concentrated on suppression of ALA-synthetase activity, and consequently, on reduced ALA and PBG production. A number of such methods of therapy have met with remarkable success and hold promise for the future treatment of the acute attack.