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Diseases of the Peripheral Nerve and Mononeuropathies
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Diana Mnatsakanova, Charles K. Abrams
Three forms associated with neuropathy: Acute intermittent porphyria (AIP): porphobilinogen deaminase deficiency.Hereditary coproporphyria (HCP): defects in coproporphyrin oxidase.Variegate porphyria (VP): impaired protoporphyrinogen oxidase.
Liver Diseases
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
The enzyme abnormality is present in the conversion of porphobilinogen to Type I and III porphyrins in the bone marrow. This abnormality is associated with a deficiency or absence of uroporphyrin isomerase.104,219 Normally the synthesis is shifted to the dominant formation of Type III porphyrins, which are used in heme synthesis. In congenital porphyria, since uroporphyrin isomerase is reduced, the amount of Type I porphyrin produced is very great, 100 mg or more per day. The Type I porphyrins are useless for the synthesis of the prosthetic groups; by not being degraded to bile pigments, they are excreted or deposited in the body. Therefore, pigmentation is a well recognized feature of the disease. In addition, photosensitivity of the skin due to porphyrins leads to various skin injuries. Compensatory mechanisms may allow the formation of normal heme, but uroporphyrin I and coproporphyrin I are markedly increased. The increase of uroporphyrin in the red cells causes hemolysis due to photosensitivity. The enhanced rate of hemolysis is compensated by an increased heme synthesis which further aggravates the condition through an increased production of Type I porphyrins as byproducts of the disease mechanism.
Sideroblastic Anemia and Porphyrias
Published in Harold R. Schumacher, William A. Rock, Sanford A. Stass, Handbook of Hematologic Pathology, 2019
As shown in Fig. 7, the synthesis of hemoglobin begins in mitochondria with the condensation of glycerin and succinylcoenzyme A to form delta aminolevulinic acid (δ ALA), a reaction catalyzed by ALA synthase. Following this mitochondrial reaction, subsequent steps in heme synthesis occur in the cytoplasm of erythroblasts. In the cytoplasm, two molecules of ALA condense to form porphobilinogen (PBG). Next, four molecules of PBG condense to form hydrox-ymethylbilane. This intermediate cycles into either urophophyrinogen I or uroporphyrinogen III.
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.
Porphyria: awareness is the key to diagnosis!
Published in Acta Clinica Belgica, 2022
Benjamin Heymans, Wouter Meersseman
The symptoms of AIP are caused by dysfunction of neurons, which are part of the sensory, autonomic, motoric, peripheral or central nervous system. Although the mechanism of this dysfunction is not completely understood, the most widely accepted view states that partial deficiency of PBD will lead to an overproduction of some neurotoxic intermediates of the haem biosynthesis [2], mainly delta-aminolevulinic acid (ALA) and porphobilinogen (PBG). There are some striking data in favour of this assumption. First, liver transplantation in a patient with AIP can result in a definitive cure [4]. Secondly, other diseases that give rise to an increase in the same neurotoxic intermediates will present with the same symptoms as AIP, such as lead poisoning and hereditary tyrosinemia type I [1].
Organophosphate insecticide poisoning with monocrotophos-induced fabricated illness in a 7-year-old girl with refractory seizures over a 4-year period
Published in Paediatrics and International Child Health, 2022
Chisambo Mwaba, Chalilwe Chungu, Ronald Chola, Kafula Lisa Nkole, Somwe Wa Somwe, Evans Mpabalwani
At the age of 4 years, the child was hospitalised for 2 months. Her clinical features were noted to be changing as she had developed new symptoms such as abdominal pain and recurrent vomiting which were reported by her mother. In addition, medical staff noted that the patient had developed non-remitting fevers and occasional tremulous movements and was passing red urine which was negative for haemoglobin and blood on urinalysis. Blood cultures were negative, as were the tuberculosis (TB) sputum cultures and Gene Xpert. The results of liver function tests (LFT) and renal function tests (RFT) were normal. The erythrocyte sedimentation rate (ESR) was 60 mm/hr (normal <10). Chest radiograph and abdominal ultrasound were also normal. A diagnosis of AIP was considered at this point, but, on testing the urine, porphobilinogen and porphyrins were not detected. However, the patient had not been having an acute attack on the day on which the urine specimens were collected. Given the recurrent fevers and high ESR and the high prevalence of TB in Zambia, a presumptive diagnosis of TB had been made. The patient was commenced on anti-tuberculous drugs which she took for a total of 6 months. In view of the possible diagnosis of AIP and the interactions between rifampicin and enzyme-inducing ASM, the ASM was changed to valproic acid.