Rhabdomyolysis & Metabolic Myopathies NGS Panel

Clinical Information

This panel may be considered in the evaluation of patients with elevated CK levels, muscle cramping and weakness, myoglobinuria, or rhabdomyolysis. The conditions included range in severity and include various forms of disorders of fatty acid and glycogen metabolism, mitochondrial disorders, muscular dystrophies, and others. Myopathic disorders presenting with leg cramps carry a risk of either rhabdomyolysis or progressive muscle weakness and can easily be missed Rhabdomyolysis results from the breakdown of skeletal muscle that may occur from a combination of environmental and genetic factors, and episodes can be triggered by a variety of factors.

Initial symptoms may occur following strenuous exercise, infections, fasting, temperature extremes, or exposure to drugs or alcohol, and the signs of rhabdomyolysis include myoglobinuria, or darkened and discolored urine, that could lead to renal failure if left untreated. Some disorders that place individuals at risk for rhabdomyolysis are characterized by a “second-wind” phenomenon where initial exercise intolerance is overcome after a short period of rest. Susceptibility to malignant hyperthermia may also present with evidence of muscle breakdown after exposure to certain anesthetics, and this condition can be life-threatening without prompt recognition and treatment.

Technical Information

This panel is performed by Next Generation Sequencing and covers the coding regions of the listed genes and the flanking intronic sequences. Promoter, 3′ untranslated sequences, and deep intronic sequences are also covered, but only known disease-causing variants in these regions will be reported. Variants identified on the panel are confirmed with Sanger sequencing if they do not meet certain quality thresholds.

Large deletions and duplications (CNVs) affecting the genes of the panel can be detected; however, due to defined settings in the analysis software, CNVs smaller than 2-kb may not be identified (for example, some small exonic level copy number changes may not be identified). Please note that certain types of genetic alterations including trinucleotide repeat expansions, methylation abnormalities, and balanced rearrangements (e.g., inversions, reciprocal translocations) may not be detected by the current analysis.

Specimen Requirements

• The preferred sample type is 3-4 ml of peripheral blood collected in an EDTA (purple top) tube. Extracted DNA and saliva are also accepted for this test. Blood and saliva kits are available by request.
• Send approximately 5µg of extracted DNA at a requested concentration of 90-130 ng/µl.
• If saliva is submitted, and the extracted DNA is below quality control, then you will be contacted to submit a blood sample or the panel can be completed on an exome backbone. Saliva samples must be submitted in an approved saliva kit.

Transport Instructions

• The blood specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.
• Extracted DNA should be sent at room temperature via overnight delivery.
• Saliva is stable at room temperature and can be delivered via overnight or ground shipping.