This program sponsored by Inozyme Pharma offers global, no-cost genetic testing for the ABCC6 gene associated with Pseudoxanthoma Elasticum (PXE). This no charge testing is being offered to patients who meet testing eligibility criteria and must be ordered by a qualified healthcare provider.
Generalized arterial calcification of infancy (also referred as Idiopathic infantile arterial calcification) is a rare infantile onset calcification of the internal elastic lamina of medium and large arteries and arterial stenosis due to myointimal proliferation (Rutsch et al. 2003. PubMedID: 12881724; Chong and Hutchins. 2008. PubMed ID: 17990935). The major early clinical features include fetal distress, heart failure, hydramnios, respiratory distress, hydrops fetalis, fetal edema, cyanosis, effusions in the pleural, peritoneal, pericardial spaces and cardiomegaly. The major late clinical features are respiratory distress, cyanosis, feeding difficulties, and heart failure (Chong and Hutchins. 2008. PubMed ID: 17990935). Without proper medical management, ~60% of the patients die from cardiovascular complications or renal artery stenosis within the first 6 months of life (Rutsch et al. 2001. PubMed ID: 11159191; Rutsch et al. 2008. PubMed ID: 20016754; Ferreira et al. 2014. PubMed ID: 25392903).
Pseudoxanthoma elasticum (PXE) is a progressive condition characterized by ectopic mineralization in elastic fibers of connective tissues mainly in skin, retina, and blood vessels. Patients may present yellowish papules in skin, progressive visual loss and cardiovascular symptoms. Cardiovascular symptoms include rupture of blood vessels particularly within the gastrointestinal tract, and early myocardial infarction (Bergen et al. 2000. PubMed ID: 10835643; Ringpfeil et al. 2000. PubMed ID: 10811882). The estimated disease prevalence is between 1/25,000 and 1/50,000 in general populations and the estimated carrier frequency is one in 111 to one in 80 individuals (Legrand et al. 2017. PubMed ID: 28102862).
The ABCC6 protein (ATP-binding cassette subfamily C member 6) coded by ABCC6 is a member of the ATP-binding cassette (ABC) protein family and serves serves as an efflux transporter and regulates plasmatic inorganic pyrophosphate (Jansen et al. 2014. PubMed ID: 24969777).
ABCC6 is the major gene involved in autosomal recessive pseudoxanthoma elasticum (Legrand et al. 2017. PubMed ID: 28102862). To date, ~350 unique pathogenic variants have been reported. They include miseense (~53%), truncating (~28%), splicing (~7%), large deletion and gross rearrangements (~11%) (Human Gene Mutation Database). A nonsense variant c.3421C>T, p.Arg1141* in exon 24 was found in 25% of cases from all ethnic backgrounds, and a large deletion involving exons 23 to 29 was found in 28% of American patients of European descent (Legrand et al. 2017. PubMed ID: 28102862).
Pathogenic ABCC6 variants have also been found in a few families with debatable autosomal dominant inheritance pattern of Pseudoxanthoma elasticum, forme fruste (Bergen et al. 2000. PubMed ID: 10835643; Bergen. 2006. PubMed ID: 16541094). No genotype-phenotype correlations have been established.
This test provides full coverage of all coding exons of the ABCC6 gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing. This test also detects the ABCC6 c.1780-29T>A and c.2248-12_2248-11del variants. Due to the homologous sequence at the region of exons 1 to exon 9 of ABCC6, we utilize a long-range PCR strategy to specifically amplify and sequence these exons, which is able to overcome the limitation of current short-read NGS technology in dealing with this type of homologous sequence (Mandelker et al. 2016. PubMed ID: 27228465).
Criteria For Test
Patient must meet ONE of the criteria below:
- Previously diagnosed PXE
- Clinical suspicion of PXE
- Healthcare providers can request collection kits for the program by clicking the "Order Test Kits" button on this page.
- Determine if the individual meets eligibility criteria and discuss the test.
- Order the test, collect the blood specimen, complete the required Test Requisition Form, and ship it to the lab.
- The genetic test will be processed at PreventionGenetics, and the results will be sent to the ordering healthcare provider within ~2 weeks after the lab receives the specimen and all appropriately completed paperwork. The ordering healthcare provider will discuss the results with the patient and/or caregiver
Turnaround time: 14 days on average upon receipt of specimen and completed paperwork at the lab.
Specimen Collection and Shipping
Collect 3 ml - 5 ml of whole blood in EDTA (purple top tube) or ACD (yellow top tube). DO NOT FREEZE. During hot weather, include a frozen ice pack in the shipping container. Place a paper towel or other thin material between the ice pack and the blood tube. In cold weather include an unfrozen ice pack in the shipping container as insulation. At room temperature, blood specimen is stable for up to 48 hours. If refrigerated, blood specimen is stable for up to one week.
Send in a screw cap tube with at least 5 μg - 10 μg of purified DNA at a concentration of at least 100 ng/μL, minimum 2 μg for limited specimens. Label the tube with the composition of the solute and DNA concentration along with the patient's name, date of birth, and/ or ID number. We only accept genomic DNA for testing; we do not accept products of whole genome amplification reactions or other amplification reactions. DNA must be extracted from a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by CAP and/or CMS. Specimens may be shipped at room temperature.
Shipping and Handling Instructions
Label all specimen containers with the patient's name, date of birth, and/or ID number. At least two identifiers should be listed on specimen containers. Specimen deliveries are accepted Monday-Saturday for all specimen types. Holiday schedules will be posted on our website at least one week prior to major holidays.