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Gene analysis Neurofibromatosis type 2 (NF2)

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Genetic testing for DMD or NF2 mutations.

₹24,420₹34,886

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Gene Analysis Neurofibromatosis Type 2 (NF2) - Comprehensive Guide

  • 1. Why is it done?
    • Test Description: This genetic test detects mutations in the NF2 gene (located on chromosome 22), which encodes the tumor suppressor protein merlin (neurofibromin 2). The test sequences the NF2 gene to identify pathogenic variants that cause Neurofibromatosis Type 2.
    • Primary Indications for Testing:
      • Clinical diagnosis of Neurofibromatosis Type 2 (bilateral vestibular schwannomas, imaging findings, family history)
      • Suspected NF2 in patients presenting with vestibular schwannomas and family history of the condition
      • Screening of at-risk family members with inherited NF2 mutations
      • Confirmation of NF2 diagnosis when clinical criteria are met
      • Risk stratification in families with known NF2 mutations
    • Timing and Circumstances:
      • Performed when NF2 is clinically suspected based on imaging findings or family history
      • Can be performed at any age after clinical evaluation and informed genetic counseling
      • Often performed in teenagers and adults with family history for early detection and surveillance planning
  • 2. Normal Range
    • Normal/Reference Result:
      • No pathogenic mutation detected in the NF2 gene
      • Wild-type NF2 gene sequence present
      • Common benign variants may be present (polymorphisms with no clinical significance)
    • Abnormal Result:
      • Pathogenic or likely pathogenic mutation identified in the NF2 gene
      • Mutations include frameshifts, nonsense mutations, splice site variants, deletions, duplications, or missense variants affecting protein function
    • Variant Classification:
      • Pathogenic: Confirmed to cause NF2 disease
      • Likely Pathogenic: Strong evidence of causing NF2 disease
      • Variant of Uncertain Significance (VUS): Unclear clinical significance, may require further investigation
      • Likely Benign: Probably does not cause NF2 disease
      • Benign: Not associated with NF2 disease
    • Units of Measurement:
      • DNA sequence analysis - qualitative report (present/absent of mutations)
      • Mutation location and description provided in standard genetic nomenclature (e.g., c.123+1G>A)
    • Interpretation Summary:
      • Normal Result: No NF2 mutation found; genetic basis for NF2 not confirmed in this patient
      • Abnormal Result: NF2 mutation present; confirms genetic diagnosis of NF2; indicates inherited predisposition to multiple nervous system tumors
  • 3. Interpretation
    • Detailed Result Interpretation:
      • Pathogenic/Likely Pathogenic NF2 Mutation Identified:
        • Confirms genetic diagnosis of NF2 (hereditary form if inherited from parent, or de novo mutation if sporadic)
        • Indicates lifelong predisposition to developing bilateral vestibular schwannomas and other nervous system tumors
        • Associated with increased risk of meningiomas, spinal tumors, optic nerve gliomas, skin tumors, and cataracts
        • Cascade genetic testing recommended for blood relatives
      • No Pathogenic Mutation Found:
        • Does not exclude NF2 diagnosis if clinical features highly suggestive; mutation may be in regulatory regions not captured by standard sequencing
        • In family members of known NF2 mutation carriers: negative result reduces but does not eliminate risk (germline mosaicism possible)
        • May warrant comprehensive imaging follow-up if clinical suspicion remains
      • Variant of Uncertain Significance (VUS):
        • Clinical significance unclear; cannot be reported as pathogenic or benign
        • Requires further clinical correlation and possible functional studies
        • May be reclassified as evidence accumulates
        • Genetic counseling recommended to discuss implications
    • Factors Affecting Test Results:
      • Germline vs. somatic mutations: germline mutations present in all cells (inherited risk), somatic mutations in specific tissues (tumor-specific)
      • De novo vs. inherited mutations: approximately 50% of NF2 cases are de novo mutations with no family history
      • Mosaicism: some individuals have the mutation in a subset of cells, potentially showing milder phenotype
      • Genotype-phenotype correlation: specific mutations may correlate with earlier onset or more severe disease manifestations
      • Penetrance and expressivity: NF2 shows nearly complete penetrance by age 60 but variable expressivity among mutation carriers
      • Quality of DNA sample and sequencing depth may affect detection of mutations
    • Clinical Significance of Result Patterns:
      • Truncating mutations (frameshifts, nonsense, splice site): high likelihood of producing nonfunctional protein; typically classified as pathogenic
      • Large deletions/duplications: frequently pathogenic; may affect dosage-sensitive regulatory regions
      • Missense mutations: variable significance; requires functional assessment and segregation analysis
      • In-frame indels: may or may not be pathogenic depending on location and effect on protein function
  • 4. Associated Organs
    • Primary Organ Systems Involved:
      • Central and Peripheral Nervous System: primary system affected, particularly the cranial and spinal nerves
      • Integumentary System (skin): prone to various skin manifestations including skin tumors and lisch nodules
      • Ocular System (eyes): affected by optic nerve gliomas, cataracts, and eyelid hamartomas
    • Medical Conditions Associated with NF2 Mutations:
      • Hallmark Tumors:
        • Bilateral Vestibular Schwannomas (acoustic neuromas): pathognomonic for NF2, typically bilateral and arise from vestibulocochlear nerves
        • Multiple Meningiomas: develop in 45-80% of NF2 patients, located intracranially or along spinal cord
        • Spinal Tumors (schwannomas, meningiomas, ependymomas): develop along spinal cord in majority of NF2 patients
      • Other Associated Tumors:
        • Optic nerve gliomas (optic pathway hamartomas/gliomas): occur in 15-25% of NF2 patients
        • Cutaneous lesions: skin tumors including schwannomas, neurofibromas, and other benign skin growths
        • Posterior subcapsular cataracts: occur early in life in 60-70% of NF2 patients
        • Eyelid hamartomas: benign growths of eyelids
        • Cerebral cavernous malformations: vascular malformations in the brain
    • Diseases Diagnosed by NF2 Gene Testing:
      • Neurofibromatosis Type 2 (NF2): autosomal dominant tumor suppressor syndrome
      • Segmental NF2: somatic mutations affecting a limited body region
      • Schwannomatosis (some cases): hereditary condition causing multiple schwannomas; some caused by NF2 mutations
    • Potential Complications Related to Tumors:
      • Hearing loss and tinnitus: from vestibular schwannomas affecting acoustic nerve function
      • Facial nerve dysfunction: facial weakness or paralysis from vestibular schwannomas or surgical intervention
      • Vision impairment: from optic nerve gliomas, cataracts, or eyelid hamartomas
      • Neurological deficits: from spinal tumors including paralysis, numbness, or bowel/bladder dysfunction
      • Increased intracranial pressure: from multiple intracranial tumors (vestibular schwannomas and meningiomas)
      • Malignancy: rare risk of malignant transformation of tumors
  • 5. Follow-up Tests
    • Recommended Follow-up Testing Based on Positive NF2 Result:
      • Imaging Studies (Baseline and Surveillance):
        • Brain MRI (with contrast): initial baseline MRI to assess for vestibular schwannomas, meningiomas, optic nerve gliomas, and cavernous malformations
        • Spine MRI (with contrast): to evaluate for spinal schwannomas, meningiomas, and ependymomas; recommended annually or every 2 years
        • Ophthalmologic examination: baseline and periodic assessment for cataracts, optic nerve gliomas, eyelid hamartomas, and Lisch nodules
        • Audiometry: baseline and periodic hearing assessments, especially in patients with vestibular schwannomas
      • Genetic Counseling and Testing of Family Members:
        • Cascade genetic testing: siblings, children, and other at-risk relatives should be offered testing if they carry the family mutation
        • Pre-test genetic counseling: to discuss inheritance pattern, testing implications, and psychological impact
        • Post-test counseling: discussion of test results, management recommendations, and support resources
      • Monitoring Frequency and Surveillance Plan:
        • Annual to biennial MRI surveillance: recommended starting in adolescence or early adulthood to detect emerging tumors early
        • More frequent imaging: may be needed for patients with growing tumors or progressive neurological symptoms
        • Annual ophthalmology exams: baseline starting in childhood, more frequent if cataracts or other findings develop
        • Annual audiology assessments: particularly important for those with vestibular schwannomas to monitor hearing function
      • Related Diagnostic Tests:
        • LZTR1 gene testing: for patients with clinical features suggestive of schwannomatosis but negative for NF2
        • SMARCB1 gene testing: for atypical presentations of schwannomatosis
        • Panel testing: multigene panel for hereditary cancer syndromes if syndromic features present
        • Genetic testing of parents: to determine if mutation was inherited or de novo (if not previously tested)
      • Specialized Consultations:
        • Neurosurgery: for evaluation and management of vestibular schwannomas and other CNS tumors
        • Otolaryngology (ENT): for hearing assessment and management of vestibular schwannomas
        • Ophthalmology: for evaluation and management of optic nerve gliomas, cataracts, and other ocular manifestations
        • Neurology: for overall neurological management and symptom monitoring
        • Clinical genetics: ongoing genetic counseling and family management coordination
  • 6. Fasting Required?
    • Fasting Requirement: NO - Fasting is not required for NF2 gene analysis
    • Sample Collection Requirements:
      • Blood sample collection: typically 3-5 mL of peripheral blood collected in EDTA tube (purple-topped tube)
      • Can be collected at any time of day without dietary restriction
      • Patient can eat, drink, and take medications as usual prior to blood draw
    • Medications:
      • No medications need to be discontinued prior to NF2 gene testing
      • Continue all regular medications as prescribed
    • Patient Preparation:
      • Informed consent: patient should understand the purpose of testing, potential results, and implications before proceeding
      • Pre-test genetic counseling: strongly recommended to discuss inheritance pattern, test limitations, and psychological implications
      • Proper identification: bring valid photo ID to ensure accurate sample identification
      • Sample labeling: correct patient information must be recorded on all tubes and test requisition forms
      • Timely processing: blood samples should be processed promptly according to laboratory protocol
    • Special Considerations:
      • Turnaround time: typically 2-4 weeks depending on laboratory complexity and whether additional testing is needed
      • Insurance authorization: verify insurance coverage before testing; some plans require prior authorization
      • Psychological preparation: consider emotional implications of positive results, especially in minors; assess family readiness for genetic information
      • Privacy and confidentiality: ensure understanding of results privacy and who will have access to genetic information

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