Kennedy Disease Repeat Expansion Analysis

Clinical Use

Use

Kennedy Disease Repeat Expansion Analysis examines the AR gene for CAG repeat expansions that lead to Kennedy disease (KD), a progressive X-linked neuromuscular disorder. Individuals affected may experience muscle weakness, atrophy, and other complications linked to lower motor neuron degeneration. Testing may be indicated for individuals with a clinical or suspected KD diagnosis, those with family history, and for carrier screening before pregnancy. The onset and severity of symptoms are directly associated with the number of CAG repeats, defining different categories such as unaffected, premutation carriers, and those with a full mutation causing Kennedy disease.

Special Instructions

Ordering the Kennedy Disease Repeat Expansion Analysis is essential for individuals exhibiting clinical signs or who have a familial predisposition. Sample collection can be performed using either a skin biopsy or EDTA blood, with specific handling and shipping conditions necessary to ensure sample integrity. Prospective patients are encouraged to consult with healthcare professionals to ascertain the appropriateness of this analysis based on personal medical history and familial risk factors.

Limitations

The primary limitation of this analysis involves the interpretation of CAG repeat counts and their clinical correlations, which may vary between individuals. Genetic counseling is recommended as results can influence clinical decisions. The potential for variable expressivity and incomplete penetrance in certain instances complicates predictive accuracy. Additionally, results may not rule out all genetic contributions to muscle weakness disorders. The sensitivity and specificity of different repeat ranges warrant careful consideration during interpretation.

Test Details

New York Approved

Methodology

PCR-based

Biomarkers

2 components

Primary ComponentCAG Repeat Expansion Analysis

Result Turnaround Time

21 days

Specimen

Tissue (Fresh)

Volume

5 cubic millimeters

Minimum Volume

5 cubic millimeters

Container

Sterile container with RPMI media or saline

Collection Instructions

Collect skin from a central location to enhance cell viability. Place the sample in a sterile container with RPMI media.

Storage Instructions

Ship at ambient temperature. Protect from excessive heat; ship in a cooled container during summer months. Specimen must arrive within 72 hours of collection.