Molecular Genetics Infantile Neuroaxonal Dystrophy, PLA2G6, Sequencing

Infantile neuroaxonal dystrophy (INAD) is a progressive neurodegenerative disorder characterized by infantile or early childhood onset of progressive motor and sensory impairment; atypical INAD presents with later onset and a more protracted course (OMIM#256600).  INAD symptoms include regression, truncal hypotonia, spastic tetraparesis, mental retardation, optic atrophy and early death.  Common pathologic features include axonal degeneration with spheroid bodies throughout the central and peripheral nervous systems and cerebellar atrophy.  Some individuals with INAD show high brain iron accumulation in the globus pallidus.  The disease is autosomal recessive and caused by mutations in the PLA2G6 gene.

Reasons for Referral

• Confirmation of clinical diagnosis in patients with classic or atypical INAD.
• Testing of family members of INAD patients with known mutations.
• Prenatal diagnosis of known familial INAD mutations.

Next generation sequencing (NGS) will analyze the exons or coding regions of three Autosomal Dominant Osteogenesis Imperfecta-associated genes using Illumina NextSeq 500/550 technology.  Samples are prepared using hybridization probes to enrich exonic regions.  This assay does not assess regions of insufficient coverage, introns and promoter regions; pseudogenes; where the reference genome is inaccurate or contains gaps and insertions; and regions of high GC or polynucleotide repeats, but may contain variants that impact gene function.

Exon-level deletion/duplication analysis is performed by running the NGS data through the Genome Analysis Toolkit (GATK) Germline Copy Number Variation best practices pipeline from GATK, version 4.1.4.1. A Bayesian model was validated clinically in our lab. The model can detect copy changes at a resolution of three (3) or more probe targets (exons) for deletions and duplications in genes that do not have pseudogenes, and is not designed to detect low-level mosaicism or balanced alterations.

Test reporting follows the American College of Medical Genetics (ACMG) guidelines.

Blood: EDTA (purple-top) or ACD (yellow-top) tube

• Adult: 6.0 mL
• Child: 3.0 mL
• Infant: 2.0-3.0 mL

Saliva: 2 ORAgene Saliva Kits (OGR-500) used according to manufacturer instructions.  Please contact KDL Client Services for a Saliva Collection Kit for patients that cannot provide a blood sample.

Assisted Saliva: 4 ORAgene Assisted Saliva Kits (OGR-575) used according to manufacturer instructions.  Please contact KDL Client Services for an Assisted Saliva Collection Kit for patients that cannot provide a blood sample.

Skin Fibroblast: Punch Biopsy (cell cultures will be prepared at KDL and used for testing), or 2 T-25 confluent flasks

Prenatal:

• Direct Amniotic Fluid (10-20mL)
• Direct CVS
• Cultured Amniocytes (2 T-25 flasks)
• Cultured CVS (2 T-25 flasks)
• Cultured Fetal Tissue: Product of Conception (2 T-25 flasks)
• Cord Blood (1-2mL)

DNA: 5-10µg at a minimum of 60-100ng/µL (DNA must be extracted in a CLIA-certified laboratory or a laboratory meeting equivalent requirements as determined by the CAP and/or CMS)

Notice Regarding Molecular Genetic Testing on CVS or Amniotic Fluid Specimens:

• Maternal cell rule-out testing will be performed on all prenatal specimens received. Please provide maternal blood in addition to the fetal specimen. Additional charges apply for the maternal cell rule-out test.

For routine testing of blood and saliva (or DNA extracted from them), KDL does NOT accept samples from patients within two (2) weeks of a packed cell/platelet transfusion or within four (4) weeks of a whole blood transfusion.  For extraordinary circumstances, where testing must be performed outside of the above windows, please contact our lab.

A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES.  Please include detailed clinical information, including ethnicity, clinical history, and family history.

Weekly

14-21 days

• Package and ship specimen to remain cold, but not frozen. 
• Ship via overnight express, using the FedEx priority overnight label provided. 
• Contact Client Services for shipping kits and instructions at (855) 535-1522.

INAD for Genetics Professionals

INAD for Primary Care Physicians

INAD Patient Brochure