The penetrance of AIP is incomplete with only 10% of gene carriers experiencing acute attacks suggesting role for other modifying genes or environment.The exact mechanism of acute attacks is not clear. The most favored hypothesis is that porpholobilinogen buildup causes a toxic effects on neurons. The autonomic and peripheral nervous system are more vulnerable than the central nervous system because they are not protected by the blood-brain barrier. This explains findings such as abdominal pain and tachycardia. Some individuals may be more likely to develop paresis based on increased susceptibility of neurons to toxins. Genetics
Inheritance
AIP has an autosomal dominant pattern of inheritance. The dominance pattern is a result of partial deficiencies from the heme biosynthesis enzymes, hydroxymethylbilane synthase  (HMBS;  EC  2.5.1.61). Due to the rarity of this disease it is difficult to estimate the prevalence of AIP and the inclusion criteria differs widely among studies causing varying statistics. AIP has a low penetrance when considering the general population, but within families the penetrance increases. This is indicative of another interaction affecting the inheritance pattern. It is speculated that this pattern is due to AIP propensity caused by the inheritance of an additional gene mutation, HMBS, in addition to other genetic and environmental influences. There have been 421 HMBS mutations that have been linked to AIP. This suggests that AIP inheritance instead follows an oligogenic or polygenic inheritance pattern.
Hematin and heme arginate is the treatment of choice during an acute attack. Heme is not a curative treatment, but can shorten attacks and reduce the intensity of an attack. Side-effects are rare but can be serious. Pain is extremely severe and almost always requires the use of opiates to reduce it to tolerable levels. Pain should be treated as early as medically possible due to its severity. Nausea can be severe; it may respond to phenothiazine drugs but is sometimes intractable. Hot water baths or showers may lessen nausea temporarily, but can present a risk of burns or falls.Seizures often accompany this disease. Most seizure medications exacerbate this condition due to their induction of cytochrome P450. Treatment can be problematic: Barbiturates and primidone must be avoided as they commonly precipitate symptoms. Some benzodiazepines are safe, and, when used in conjunction with newer anti-seizure medications such as gabapentin, offer a possible regimen for seizure control. Society
One of the many hypothesized diagnoses of the artist Vincent van Gogh is that he and his siblings, in particular his brother Theo, had AIP and syphilis. Another theorized case was King George III of the United Kingdom who even had a medallion struck to commemorate his "curing". His descendant Prince William of Gloucester was reliably diagnosed with variegate porphyria in 1968. It is probable that the philosopher Jean-Jacques Rousseau had porphyria. It has even been suggested that Vlad III, Prince of Wallachia, more commonly known by his surname Dracula, had porphyria. References


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