Recurrent Rhabdomyolysis: When to Suspect a Genetic Cause

When a patient presents with recurrent episodes of rhabdomyolysis and a thorough workup fails to identify a clear cause—such as trauma, infection, or toxins—an underlying genetic condition should be strongly considered. These cases of idiopathic recurrent rhabdomyolysis can represent a significant diagnostic challenge, leaving both clinicians and patients without answers or a clear management plan.

A systematic genetic workup can be the key to resolving this diagnostic odyssey. By identifying a pathogenic variant in a known disease-causing gene, clinicians can move from a state of uncertainty to one of diagnostic clarity, enabling personalized care and informed counseling.

Frequently asked questions

When is genetic testing indicated for rhabdomyolysis?

Genetic testing is indicated for patients with recurrent episodes of rhabdomyolysis, especially when common acquired causes have been excluded. A positive family history or the presence of other syndromic features further strengthens the indication for a genetic workup.

What genetic conditions can cause recurrent rhabdomyolysis?

A wide range of inherited disorders can present with rhabdomyolysis. The most common categories include disorders of fatty acid oxidation (e.g., CPT2 deficiency), glycogen storage diseases (e.g., McArdle disease), muscular dystrophies, and malignant hyperthermia susceptibility (e.g., RYR1-related myopathies).

How does a genetic diagnosis impact patient management?

A definitive diagnosis allows for targeted management strategies. This may include strict avoidance of triggers like prolonged exercise or fasting, specific dietary modifications, surveillance for cardiac or respiratory complications, and avoiding certain anesthetic agents in cases like malignant hyperthermia.

The Diagnostic Challenge of Idiopathic Rhabdomyolysis

The initial workup for rhabdomyolysis correctly focuses on identifying and removing precipitating factors. However, in a subset of patients, episodes recur without an obvious trigger. This clinical scenario suggests an intrinsic muscle vulnerability, where a normally tolerated stressor (e.g., moderate exercise, fever) is sufficient to induce massive muscle damage.

Without a unifying diagnosis, patients may undergo repeated, costly hospitalizations and extensive, often unrevealing, investigations. The diagnostic uncertainty can also lead to anxiety for patients and their families, who are left without an understanding of the underlying cause or how to prevent future episodes. This is where a genetic approach becomes essential.

Key Genetic Culprits in Recurrent Rhabdomyolysis

The genetic architecture of rhabdomyolysis is heterogeneous, involving dozens of genes related to muscle energy metabolism, structural integrity, and calcium homeostasis. Broadly, these can be grouped into several major categories.

Metabolic Myopathies

Disorders of muscle energy metabolism are a primary cause of exertional or stress-induced rhabdomyolysis. The muscle’s inability to meet energy demands during stress leads to cell breakdown.

• Fatty Acid Oxidation Defects: Carnitine palmitoyltransferase II (CPT2) deficiency is a classic example, where prolonged exercise, fasting, or illness can trigger episodes.
• Glycogen Storage Diseases: McArdle disease (Glycogen Storage Disease Type V), caused by mutations in the PYGM gene, impairs the breakdown of glycogen for energy, leading to exercise intolerance and rhabdomyolysis.

Muscular Dystrophies

While often associated with progressive muscle weakness, some muscular dystrophies can present initially with recurrent rhabdomyolysis before weakness becomes the dominant feature. Pathogenic variants in the DMD gene can cause a spectrum from Duchenne to Becker muscular dystrophy, with rhabdomyolysis being a known feature. Many limb-girdle muscular dystrophies (LGMDs) can also have a similar presentation.

Malignant Hyperthermia Susceptibility and Channelopathies

Mutations in genes controlling muscle calcium channels, such as the ryanodine receptor 1 gene (RYR1), are well-known causes of malignant hyperthermia. However, these variants can also cause a broader myopathy with non-anesthetic triggers like heat or exercise, leading to rhabdomyolysis.

The Clinical Utility of a Genetic Diagnosis

Securing a molecular diagnosis through genetic testing provides immediate and long-term clinical value. The benefits are multifaceted:

• Ending the Diagnostic Odyssey: A definitive result provides an answer, preventing further unguided and potentially invasive testing, such as muscle biopsy.
• Informing Management: Treatment becomes precise. A patient with CPT2 deficiency will be counseled on avoiding fasting and consuming a high-carbohydrate diet, while a patient with malignant hyperthermia susceptibility receives critical information about anesthetic risks.
• Prognostic Guidance: The specific gene and variant can inform the likely clinical course, including the risk of progressive weakness or involvement of other organ systems like the heart.
• Family Counseling: It allows for discussion of inheritance patterns, reproductive options, and facilitates cascade carrier testing for at-risk relatives, who may be asymptomatic but still at risk.

When to Proceed with Genetic Testing

For any patient with recurrent rhabdomyolysis of unknown etiology, a genetic workup is a logical next step. Modern approaches like whole exome or whole genome sequencing offer a comprehensive and efficient method to assess a wide range of potential causative genes simultaneously. This broad analysis is often more effective than sequential single-gene or panel testing given the extensive genetic heterogeneity.

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