Porphyria Genotyping

Description: 
King’s College Hospital is a Supra-Regional Assay Service for the porphyrias and encompasses a porphyrins laboratory, genetic service and porphyria clinic. The Molecular Diagnostics Laboratory provides the genetic testting service.

ASSAYS AVAILABLE

++ HMBS Sanger Sequencing for Acute Intermittent Porphyria

Acute Intermittent Porphyria (AIP) is the commonest form of the acute hepatic porphyrias and is caused by pathogenic variants in the HMBS gene.
All 15 exons and the promoter region of the HMBS gene are amplified in 12 amplicons. 5’ and 3’ primers specific for each amplicon are used to amplify the regions. Each of the primers carries an M13 F or R tag to ensure the entire product can be sequenced.

++ PPOX Sanger Sequencing for Variegate Porphyria

Variegate Porphyria (VP) is one of the acute porphyrias and is caused by pathogenic variants in the PPOX gene. VP is about one-third as prevalent as Acute Intermittent Porphyria (AIP) in most European countries but is more common in South Africa.
All 13 exons and the promoter region of the PPOX gene are amplified in 13 amplicons. 5’ and 3’ primers specific for each amplicon are used to amplify the regions. Each of the primers carries an M13 F or R tag to ensure the entire product can be sequenced.

++ Variegate Porphyria PPOX Gene R59W Detection

In South Africa the incidence of variegate porphyria (VP) is approx. 3 in 1000 with the c.175C>T; p.Arg59Trp variant in the PPOX gene being responsible for the vast majority of these cases. In the UK the incidence is much lower, however this is still the most commonly searched for variant in a patient presenting with possible variegate porphyria.
The relevant region of the PPOX genomic sequence is PCR-amplified. Mutant and wild type sequences are differentiated by specific fluorescently labelled probes. TaqMan PCR is used for this purpose.

++ Red Cell Gene Panel: Porphyria Subpanel.

Comprehensive sequencing service for all the known genes associated with porphyria is available in a single next-generation sequencing panel. Full gene coverage including all exons +/- 50bp intron/exon boundaries.

Genes: ALAD , ALAS2 , CPOX , FECH , GATA1 , HMBS , PPOX , UROD , UROS

For more information, please visit the Red Cell Gene Panel (RCGP) test page.
Clinical details: 
The porphyrias are a group of mainly inherited diseases affecting the haem synthesis pathway that can be divided into two groups based on their clinical symptoms. The acute porphyrias include acute intermittent porphyria (AIP), hereditary coproporphyria (HCP) and variegate porphyria (VP). The biochemical hallmark of an acute porphyria attack is the increase in urine excretion of porphobilinogen (PBG) that increases to more than 10 times the upper limit of normal during an attack1. However, urinary PBG concentrations may return to normal during remission, particularly in VP and HCP, and can be misleading in patients who have never experienced an attack. Biochemical analysis is thus only reliable in patients who have recently had clinical symptoms of an attack.
Reference range: 

 

Sample type and Volume required: 
Volume of blood anticoagulated with EDTA: Adult and children 4 ml, Infants (0-2 years) 1 ml
Clotted samples are unsuitable for DNA analysis.
Blood Samples in in correct anticoagulant tubes may be rejected.
We accept DNA samples. Please provide at least 1-5µg of purified DNA
For prenatal diagnosis please refer to section for sample requirements.
Turnaround time: 
40 working days
Storage and transport: 
Blood should be stored at 4°C where possible. Send at room temperature by first class post. If possible, please complete the request form attached and send as a hard copy (do not send electronically) with the sample. This will ensure all relevant information is available and will aid us in processing your test.
Contacts:
Red Cell Centre - Molecular Diagnostics Laboratory
020 3299 1246 / 2265
kch-tr.pnd@nhs.net
c/o Central Specimen Reception
Blood Sciences Laboratory
Ground Floor Bessemer Wing
King’s College Hospital
Denmark Hill
London SE5 9RS
Mon-Fri, 9.00am-5.30pm
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 15/01/2020