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FSHD Type 1 Testing (D4Z4 repeat size)

Omics test Model
Test Code D8000
Test Summary

This test provides D4Z4 repeat size and 4q haplotype.

Turn Around Time 3 - 5 weeks
Acceptable Sample Types Whole Blood, Refrigerated (EDTA)
Acceptable Billing Types Institutional Billing , Self (patient) Payment
NY Approved Yes
Self (patient) Price $1,300.00
Institutional Price $1,300.00
CPT Codes** 81404(x2)
*TAT starts after the sample and all required sample information is received at the processing laboratory.

**The CPT codes listed are in accordance with Current Procedural Terminology, a publication of the American Medical Association, and are provided for informational purposes only. CPT coding is the sole responsibility of the billing party.

This testing service has not been cleared or approved by the U.S. Food and Drug Administration. Testing services may not be licensed in accordance with the laws in all countries. The availability of specific test offerings is dependent upon laboratory location.

Test Description

This test utilizes Whole Genome Optical Mapping technology to accurately detect the D4Z4 repeat sizes on chromosomes 4 and 10 to within +/- 1 repeat and perform haplotyping of the 4q alleles.

Indications for Testing

  • Molecular confirmation of a clinical diagnosis of FSHD
  • Clinical suspicion of FSHD and previous neuromuscular panel did not yield a diagnosis

Condition Description

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by muscle weakness and wasting. This condition gets its name from the muscles that are affected most often: those of the face (facio-), around the shoulder blades (scapulo-), and in the upper arms (humeral). The signs and symptoms of FSHD usually appear in adolescence. However, the onset and severity of the condition vary widely. Milder cases may not become noticeable until later in life, whereas rare severe cases become apparent in infancy or early childhood. Weakness involving the facial muscles or shoulders is usually the first symptom of this condition. Facial muscle weakness often makes it difficult to drink from a straw, whistle, or turn up the corners of the mouth when smiling. Weakness in muscles around the eyes can prevent the eyes from closing fully while a person is asleep, which can lead to dry eyes and other eye problems. For unclear reasons, weakness may be more severe on one side of the face than the other. Weak shoulder muscles tend to make the shoulder blades protrude from the back, a common sign known as scapular winging. Weakness in the shoulders and upper arms muscles can make it challenging to raise the arms over the head or throw a ball. The muscle weakness associated with FSHD worsens slowly over decades and may spread to other body parts. Weakness in muscles of the lower legs can lead to a condition called foot drop, which affects walking and increases the risk of falls. Muscular weakness in the hips and pelvis can make climbing stairs or walking long distances difficult. Additionally, affected individuals may have an exaggerated lower back curvature (lordosis) due to weak abdominal muscles. About 20 percent of affected individuals eventually require the use of a wheelchair. Additional signs and symptoms of FSHD include mild high-tone hearing loss and retinal abnormalities. These signs are often not noticeable and may only be discovered during medical testing. FSHD rarely affects the heart or respiratory muscle. Researchers have described two types of FSHD: type 1 (FSHD1) and type 2 (FSHD2). Both types have the same signs and symptoms and are only distinguished by their genetic cause.

Test Methods and Limitations

The Bionano EnFocus FSHD Analysis is performed based on whole-genome optical mapping data collected on the Bionano Genomics Saphyr Genome Imaging Instrument. Based on specific labeling and mapping of ultra-high molecular weight DNA in nanochannel arrays, optical mapping enables high-resolution analysis of the D4Z4 repeat array. Molecules aligning to regions of interest in chr4 and chr10 are extracted and assembled. The resulting consensus maps are used for the Bionano EnFocus FSHD Analysis. The repeat arrays are sized, and the permissive and non-permissive alleles (4qA and 4qB) are assigned. This method cannot detect single-nucleotide variants that do not impact sequence motif sites and may miss small variants with potential functional impacts.

Detailed Sample Requirements

Whole Blood, Refrigerated (EDTA)
Test Details Page
Sample Condition Blood should be collected in EDTA tubes (e.g. BD Sciences, Catalog# 366450) and refrigerated as soon as possible after collection. The sample should be shipped at refrigeration temperature and include an ice pack within the box. Do not freeze the specimen. Please note that shipping conditions can dramatically affect the temperature of the sample while in transit. If using a Revvity Omics collection pack, please package the specimen in the provided box and activate the included coolant pack.
Shipping

All samples should be shipped to the lab on the same day of the draw. Due to the time-sensitive nature of this test, the sample must arrive in the lab within five days of collection. Please include a completed requisition form marked with the appropriate FSHD order to avoid delays in processing. Date of Collection is a REQUIRED field.