Acute intermittent porphyria.
ABSTRACT Acute intermittent porphyria (AIP) is characterised by neurovisceral crises the most common clinical presentation of which is abdominal pain. It is an autosomal dominant condition with incomplete penetrance and is potentially life-threatening. The key point in management is to suspect and confirm the diagnosis as early as possible in order to treat the attack and to avoid inappropriate treatments which may exacerbate the crisis. In this chapter we briefly outline the haem biosynthetic pathway and how deficiencies in individual enzymes give rise to the different porphyrias. We then describe the clinical features and diagnosis of AIP, followed by a discussion of pathogenesis, highlighting advances in the molecular biology of AIP and introducing the debate as to whether neurovisceral crises might result from porphyrin precursor neurotoxicity or from haem deficiency. Finally we discuss management, including family screening, avoidance of triggering factors, analgesia, maintenance of a high calorie intake, and administration of haem derivatives.
- SourceAvailable from: scielo.br[Show abstract] [Hide abstract]
ABSTRACT: Porphyrias are metabolic disorders related to heme biosynthesis pathway enzyme dysfunctions. The heme pathway is fundamental for the formation of a number of molecules, and such defects cause noxious precursors (porphyrins) to build up. Porphyrias are heterogeneously manifested by symptoms that can either be neurovisceral, cutaneous, or both, usually during outburst episodes called porphyric crises. This article presents a literature review and reports on a case of porphyric crisis initially diagnosed as acute abdomen and treated with an inconclusive exploratory laparotomy During the postoperative period, the patient progressed with tetraparesis, tetraplegia and respiratory distress, suggesting Guillain-Barre syndrome, which was precluded after cerebrospinal fluid analysis revealed no albumin-cytological dissociation. The patient was admitted to the intensive care unit due to her neurological disorders, which required ventilation support. After admission, she progressed with choluria and seizures. A porphyric crisis was suspected and confirmed upon a 24 hour urine porphyrins test. Supportive therapy was initiated, but due to unavailability in our hospital, heme derivatives were not given. The patient progressed with nosocomial infection, organ dysfunctions and eventually died. Porphyria should be considered as a differential diagnosis in acute abdomen cases of unknown origin and associated with neurological disorders such as paresis, hydroelectrolytic and psychiatric disorders, especially in patients with triggering factors, with a history of recurring crises and a family history of porphyria.Revista brasileira de terapia intensiva. 12/2011; 23(4):510-514.
- [Show abstract] [Hide abstract]
ABSTRACT: Objective: The Norwegian Porphyria Centre routinely offers genetic counselling and predictive genetic testing in families diagnosed with porphyria. The aim of this study was to investigate the subjective experiences of adolescents and young adults who were genetically tested for acute intermittent porphyria (AIP) as minors. What were the psychosocial consequences and how were these handled? Methods: Qualitative interviews of ten Norwegians aged 16-21 years were performed and analysed based on interpretive description. All participants were initially predictively tested for AIP as minors, but three had subsequently developed manifest disease. Results: The participants considered early diagnosis and lifestyle moderation advantageous, but finding motivation for precaution was difficult. AIP inflicted few psychosocial challenges and was a small part of the participants' identity, but risk of manifest disease was, nevertheless, a cause for concern for two participants with latent AIP. The participants were content with their present level of knowledge and they felt capable of obtaining relevant information when needed. AIP was experienced as a vague condition, and participants and their relatives attributed a variety of symptoms to the disease. Conclusion and implications: Being genetically tested as a minor was experienced as useful and entailed relatively few adverse psychosocial consequences, although there was a potential for concern. Appropriate and individually tailored genetic counselling and written consent is subsequently advised. What constitutes a suitable age for testing will differ from individual to individual, but these results suggest that parents in collaboration with their children may be suited to decide what age is appropriate.JIMD reports. 01/2011; 1:1-7.
- [Show abstract] [Hide abstract]
ABSTRACT: The autosomal dominantly inherited disease acute intermittent porphyria (AIP) is caused by mutations in hydroxymethylbilane synthase (HMBS, or porphobilinogen deaminase), the third enzyme in the haem biosynthesis pathway. Enzyme-intermediates with increasing number of porphobilinogen (PBG) molecules are formed during the catalysis of HMBS. In this work we studied the two uncharacterised mutants K132N and V215E comparative to wild-type (wt) HMBS and to the previously reported AIP-associated mutants R116W, R167W and R173W. These mainly present defects in conformational stability (R116W), enzyme kinetics (R167W) or both (R173W). A combination of native PAGE, circular dichroism, differential scanning fluorimetry, and ion-exchange chromatography were used to study conformational stability and activity of the recombinant enzymes. We also investigated the distribution of intermediates corresponding to specific elongation stages. It is well known that the thermostability of HMBS increases when the dipyrromethane cofactor binds to the apoenzyme and the holoenzyme is formed. Interestingly, a decrease in thermal stability was measured concomitant to elongation of the pyrrole chain, indicating a loosening of the structure prior to product release. No conformational or kinetic defect was observed for the K132N mutant, while V215E presented lower conformational stability and probably a perturbed elongation process. This is in accordance with the high association of V215E with AIP. Our results contribute to interpret the molecular mechanisms for dysfunction of HMBS mutants and to establish genotype-phenotype relations for AIP.Bioscience Reports 07/2013; · 1.88 Impact Factor