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Charcot-Marie-Tooth Type 4B2 via the SBF2 Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
SBF2 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
11637SBF281479 81479,81479 $990 Order Options and Pricing

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

Turnaround Time

3 weeks on average for standard orders or 2 weeks on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.


Genetic Counselors


  • Angela Gruber, PhD

Clinical Features and Genetics

Clinical Features

Charcot Marie Tooth disease (CMT), also known as hereditary motor and sensory neuropathy (HMSN), is a large group of inherited disorders of the peripheral nerves. The progressive degeneration of motor nerves results in weakness and atrophy of the distal muscles; and the degeneration of sensory nerves leads to decreased sensation, tingling and numbness in the legs, feet, arms and hands and neuropathic pain. The age of onset varies from childhood to mid adulthood. Symptoms usually begin with weakness and atrophy in the muscle of the legs and feet. As the disease progresses, weakness and atrophy of the muscles of the arms and hands may occur. CMT is heterogeneous in regards to symptoms, severity and progression rate. Although the disease may lead to disability and respiratory difficulty, life expectancy is usually unaffected. Most common symptoms include foot deformity, loss of balance, hammertoes, foot drop, frequent tripping and falls, and reduced manual dexterity. Diagnosis is based on clinical features, family history, neurological examination, electromyography (EMG), and nerve conduction velocity (NCV) findings (Pareyson and Marchesi, 2009. PubMed ID: 19539237; Bird, 2015. PubMed ID: 20301532). CMT affects approximately 1 in 3,300 people.

Charcot-Marie-Tooth type 4B2 (CMT4B2) is a demyelinating form of CMT that primarily affects the myelin sheath of the peripheral nerve. Patients with CMT4B2 will exhibit the typical slow nerve conduction velocities (NCV) of a demyelinating neuropathy, distal muscle weakness and atrophy, depressed deep tendon reflexes, foot deformities such as hammertoes and pes cavus, and sensory impairment (Azzedine et al., 2003. PubMed ID: 12687498; Hirano et al., 2004. PubMed ID: 15304601). Sural nerve biopsy will show myelin outfoldings, which are a hallmark of CMT4B. Of note, some cases have also presented with early onset glaucoma (Hirano et al., 2004. PubMed ID: 15304601; Chen et al., 2014. PubMed ID: 25462154). The onset is typically in the first to second decade of life.


Charcot-Marie-Tooth type 4B2 (CMT4B2) is inherited in an autosomal recessive manner due to pathogenic variants in SBF2, located on chromosome 11p15.4. The SBF2 gene encodes myotubularin-related protein 13 also called set-binding factor 2. The SBF2 protein has been shown to interact with MTMR2 and regulates the enzymatic activity; however, the exact cellular role is not fully understood. Thus far, reported pathogenic variants include missense, nonsense, splicing and small deletions that result in a frameshift and premature protein termination (Human Gene Mutation Database).

Clinical Sensitivity - Sequencing with CNV PGxome

Clinical sensitivity cannot be estimated because only a small number of patients have been reported. However, pathogenic variants in SBF2 appear to be a rare cause of disease. Analytical sensitivity should be high because almost all reported pathogenic variants thus far are detectable by sequencing.

Thus far, only two large deletions involving the SBF2 gene have been reported (Human Gene Mutation Database).

Testing Strategy

This test provides full coverage of all coding exons of the SBF2 gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

Individuals with clinical symptoms consistent with Charcot-Marie-Tooth and autosomal recessive inheritance. Testing is also indicated for family members of patients who have known SBF2 pathogenic variants. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in SBF2.


Official Gene Symbol OMIM ID
SBF2 607697
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Charcot-Marie-Tooth Disease, Type 4B2 AR 604563


  • Azzedine et al., 2003. PubMed ID: 12687498
  • Bird, 2015. PubMed ID: 20301532
  • Chen et al., 2014. PubMed ID: 25462154
  • Hirano et al., 2004. PubMed ID: 15304601
  • Human Gene Mutation Database (Bio-base).
  • Pareyson and Marchesi, 2009. PubMed ID: 19539237


Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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Note: acceptable specimen types are whole blood and DNA from whole blood only.
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