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Clinical Chemistry
Published in Paul Bentley, Ben Lovell, Memorizing Medicine, 2019
Hepatic porphyrias are commoner than erythropoietic porphyrias, even though 85% of body haem is synthesized in RBC, because in the liver, haem production is controlled by negative feedback, and so a failure to produce haem increases the rate of porphyrin production
Porphyric Red Cells
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
One classification of the porphyrias divides them into hepatic, erythropoietic, or a combination of both (Table 1). All the hepatic porphyrias, except porphyria cutanea tarda, have an “acute” symptomatology with abdominal pains, and neurologic and pyschiatric disturbances. This is due to overproduction of delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) in the body. ALA and PBG in some way interfere with neuron and this probably leads to the different symptoms in these diseases. The acute symptoms of these diseases are also easily elicited by a number of different drugs.9 All the porphyrias, except for acute intermittent porphyria and the newly discovered ALA-dehydratase deficiency,10 have cutaneous symptoms due to accumulation of porphyrins in the skin. When the porphyrins are exposed to light around 400 nm they become excited and react with molecular oxygen which in turn is excited to singlet oxygen; this activated form of oxygen is responsible for the subsequent oxidative tissue damage.
Psychiatric Misdiagnosis
Published in Mark S. Gold, R. Bruce Lydiard, John S. Carman, Advances in Psychopharmacology: Predicting and Improving Treatment Response, 2018
The porphyrias are rare, inborn errors of metabolism which are transmitted in an auto-somonal dominant pattern.15,75–84 They represent a group of diseases in which there is an excess excretion of porphyrin precursors. There are two types of porphyrias; the first type results from excess accumulation of porphyrin precursors in bone marrow and blood forming cells. The second kind are the hepatic porphyrias, which include acute intermittent porphyria, hereditary coproporphyria, and porphyria veraigata, which produces skin lesions. All of the hepatic porphyrias can present with psychiatric symptoms, but acute intermittent porphyria is the most common.15,75–84
Current understanding of the etiology of cyclic vomiting syndrome and therapeutic strategies in its management
Published in Expert Review of Clinical Pharmacology, 2022
Rosita Frazier, Thangam Venkatesan
Testing for CVS should generally be limited to upper endoscopy and abdominal imaging to rule out organic pathology such as gastric volvulus or intermittent small bowel obstruction. Biochemical testing including CBC, basic chemistry panel, amylase, lipase, and liver tests may be performed. Gastric emptying can be normal, delayed, and often rapid in CVS and is not recommended. Extensive testing should be avoided and only pursued in the appropriate clinical setting [56,57]. For example, brain imaging might be considered in patients with localized neurological symptoms. In the appropriate setting, other conditions such as acute hepatic porphyria which can have a similar clinical presentation might be considered. In this scenario, testing with a spot urine porphobilinogen and aminolevulinic acid should be done. If hypoglycemia or hyponatremia is noted, testing for adrenal insufficiency is recommended. In children, investigations to rule out urea cycle defects are recommended when episodes are triggered by fasting, intercurrent illness, or high protein meals.
Givosiran, a novel treatment for acute hepatic porphyrias
Published in Expert Review of Precision Medicine and Drug Development, 2021
Manish Thapar, Sean Rudnick, Herbert L. Bonkovsky
The human porphyrias generally are classified according to the principal sites of overproduction of porphyrins or porphyrin precursors as being either hepatic or erythropoietic. The hepatic porphyrias are further classified as being ‘acute’ or ‘inducible’ (due to up-regulation of ALA synthase-1) or as being ‘chronic.’ The acute designation is used for four relatively rare disorders, all due to inherited defects in normal heme synthesis [ALA dehydratase deficient porphyria (ADP); acute intermittent porphyria (AIP), due to partial deficiency of HMBS; hereditary coproporphyria (HCP), due to partial deficiency of CPOX; and variegate porphyria (VP), due to partial deficiency of PPOX]. When these are biochemically active (elevated ALA and PBG), there is induction of ALA synthase-1 in the liver, as already described, leading to marked overproduction of ALA, and usually also of porphobilinogen (PBG). The chronic hepatic porphyrias comprise two disorders, porphyria cutanea tarda (PCT) and hepatoerythropoietic porphyria (HEP), which, respectively, are due to partial (∼50%) or nearly total (>90%) deficiency of uroporphyrinogen decarboxylase (UROD), the fifth enzyme of the heme synthetic pathway. PCT, the disorder with milder UROD deficiency, occurs mainly in adult men with underlying liver disease, whereas the disorder with severe UROD deficiency is HEP. It is usually manifest in childhood or infancy and continues life-long.
Cost savings with hemin versus givosiran for the treatment of patients with acute intermittent porphyria (AIP)
Published in Journal of Medical Economics, 2020
Samira Massachi, Josh Epstein, Julie Hurd, Herbert L. Bonkovsky
Acute hepatic porphyrias (AHP) comprise a rare set of four genetic conditions, which are genetically distinct but have in common the overproduction of heme precursors1,2. The most common form of AHP is known as acute intermittent porphyria (AIP), a metabolic disorder characterized by deficiency of the enzyme hydroxymethylbilane synthase (HMBS; also known as porphobilinogen deaminase, PBGD)3,4. Estimates of HMBS deficiency prevalence in the general population have varied from 1/12995 to 1/16756 to 1/17827 people, while symptomatic disease penetrance has been estimated to be 0.5–1% of the people with HMBS deficiency5,7.