Necrotizing myopathy

Earlier identification and treatment initiation

Necrotizing autoimmune myopathy is a disease that causes severe muscle weakness. Timely diagnosis and treatment is important to improving outcomes, but differentiating NAM from other myopathies on initial clinical assessment may be difficult because:

  • A clinical presentation of proximal limb weakness in association with an elevated serum creatinine kinase may not be specific to NAM.
  • A muscle biopsy may be confounded by the presence of overlapping histopathological features with other myopathies.

Therefore, a positive HMGCR-IgG or SRP-IgG autoantibody result will aid in achieving a shorter time to diagnosis and assist with sorting out these diagnostic challenges.


of NAM patients will be seropositive for HMGCR-IgG or SRP-IgG

An advanced approach to diagnosis

We offer improved clinical assay performance through:

  • A single evaluation with the two most pertinent antibodies associated with NAM: HMGCR-IgG and SRP-IgG. The combination of both antibodies maximizes clinical sensitivity for diagnosing patients with this disease.
  • Detection of SRP-IgG using a sensitive immunofluorescence-based assay and then confirming by a second immunoblot technology.
  • Antibodies are tested in parallel, providing results within a week.

Which test should I order?

A Test in Focus

Christopher Klein, M.D., gives an overview of the necrotizing myopathy evaluation. He discusses when this testing should be ordered, how this testing compares to previous testing approaches, and what clinical action can be taken due to the results of this testing.

Learn more about how to order this evaluation at your institution.

Additional resources

Improved diagnosis of necrotizing autoimmune myopathy by combinatorial immune assays

This “Specialty Testing” webinar, presented by Christopher Klein, M.D., discusses the diagnosis, pathological understanding, and current best treatment options for necrotizing autoimmune myopathy.

A world of differenceDavid Voeltz

In late 2019, after months of looking for a reason for his rapid loss of muscular function, David Voeltz got an answer: he had necrotizing autoimmune myopathy. Today, after nearly two years of treatment, David has a renewed lease on life and keen appreciation for the Mayo Clinic team that confirmed his diagnosis.