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GTR Home > Conditions/Phenotypes > Acute intermittent porphyria

Acute intermittent porphyria

Synonyms
Acute Porphyria; HMBS deficiency; Hydroxymethylbilane Synthase Deficiency; Porphobilinogen deaminase deficiency; Porphyria, Swedish type; UPS deficiency; Uroporphyrinogen synthase deficiency
Modes of inheritance
Autosomal dominant inheritance (Orphanet)

Summary

Excerpted from the GeneReview: Acute Intermittent Porphyria
An acute porphyria attack is characterized by a urine porphobilinogen (PBG)-to-creatinine ratio ≥10 times the upper limit of normal (ULN) and the presence of ≥2 porphyria manifestations (involving the visceral, peripheral, autonomic, and/or central nervous systems) persisting for >24 hours in the absence of other likely explanations. Onset of acute attacks typically occurs in the second or third decade of life. Acute attacks are more common in women than men. Although attacks in most individuals are typically caused by exposure to certain endogenous or exogenous factors, often no precipitating factor can be identified. The course of acute porphyria attacks is highly variable in an individual and between individuals. Recovery from acute porphyria attacks may occur within days; however, recovery from severe attacks that are not promptly recognized and treated may take weeks or months. The five categories of acute intermittent porphyria (AIP), caused by a heterozygous HMBS pathogenic variant, are based on the urine PBG-to-creatinine ratio and occurrence of acute attacks. Active (symptomatic) AIP: An individual who has experienced at least one acute attack within the last two years. Symptomatic high excreter: Urine PBG-to-creatinine ratio ≥4 times ULN and no acute attacks in the last two years but chronic long-standing manifestations of acute porphyria. Asymptomatic high excreter: Urine PBG-to-creatinine ratio ≥4 times ULN and no acute attacks in the last two years and no porphyria-related manifestations. Asymptomatic AIP: Urine PBG-to-creatinine ratio <4 times ULN and no acute attacks in the last two years but has had ≥1 acute attack in the past. Latent (inactive) AIP: Urine PBG-to-creatinine ratio <4 times ULN and no acute porphyria-related manifestations to date.
Full text of GeneReview (by section):
Summary
GeneReview Scope
Diagnosis
Clinical Characteristics
Genetically Related (Allelic) Disorders
Differential Diagnosis
Management
Genetic Counseling
Resources
Molecular Genetics
Chapter Notes
References
Authors:
Eliane Sardh
Michela Barbaro
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Clinical tests (58 available)

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  • Also known as: ENCEP, LENCEP, PBG-D, PBGD, PORC, UPS, HMBS
    Summary: hydroxymethylbilane synthase

Clinical features

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Imported from Human Phenotype Ontology (HPO)

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