Can Anti-SRP IMNM Cause Heart and Lung Complications?

Yes, if you have the anti-SRP subtype of immune-mediated necrotizing myopathy (IMNM), you should discuss cardiac (heart) and pulmonary (lung) evaluation with your neuromuscular or rheumatology team. While IMNM is primarily a muscle disease, the anti-SRP subtype is known to involve the heart and lungs in some patients ^[1][2][3]. Specialist referral and repeat testing should be individualized based on your symptoms, examination, disease severity, and initial test results. Baseline screening is often appropriate to identify any treatable problems early, but this does not mean you inevitably have heart or lung disease ^[4][5].

Urgent Symptoms to Watch For
Seek emergency medical evaluation if you experience:

• New or worsening chest pain or pressure
• Severe or rapidly worsening breathlessness, or inability to speak or lie flat due to breathlessness
• Fainting, confusion, or blue/gray lips
• A sustained fast or irregular heartbeat accompanied by dizziness or feeling unwell

Cardiac (Heart) Complications

Research indicates that patients with anti-SRP IMNM may be vulnerable to heart complications, although the exact frequency varies across different studies and patient groups ^[5][2]. When heart issues do occur, they can include:

• Myocarditis and Cardiomyopathy: Inflammation of the heart muscle or changes in the heart’s pumping ability ^[1][6].
• Arrhythmias: Irregular heartbeats or conduction blocks affecting the heart’s electrical system ^[7][8].
• Diastolic Dysfunction: Increased stiffness of the heart muscle, meaning it does not relax normally between beats ^[6][8].
• Heart Failure: Infrequently, acute heart failure can occur ^[7].

Cardiac Assessment

Your doctor may recommend a baseline cardiac assessment to establish your normal function and check for silent issues:

• Electrocardiogram (EKG/ECG) & Echocardiogram: An EKG checks your heart’s electrical activity, while an echocardiogram is an ultrasound that evaluates pumping function and checks for diastolic dysfunction ^[4][9].
• Blood Biomarkers: Tests like Troponin I and BNP/NT-proBNP can indicate heart strain or injury. While Troponin T can be elevated simply due to your skeletal muscle damage from IMNM, Troponin I is often preferred to help distinguish heart injury from muscle injury ^[4][10]. However, doctors interpret these alongside your symptoms and other tests, as no single blood test provides a perfect diagnosis.
• Cardiac MRI (CMR): If symptoms, an EKG, or an echocardiogram suggest heart involvement, a Cardiac MRI is a sensitive test used to detect inflammation or scarring in the heart tissue ^[5][11]. It is not routinely required for all asymptomatic patients.

Pulmonary (Lung) Complications

Lung involvement is a notable concern for some individuals with anti-SRP IMNM. Symptoms like breathlessness or fatigue can have many causes—including muscle weakness, anemia, infection, or medication effects—so it is important not to self-diagnose based on symptoms alone.

Complications can include:

• Interstitial Lung Disease (ILD): A group of conditions that cause inflammation and scarring (fibrosis) of the lung tissue. While some specialized cohort studies have reported ILD in up to 45% to 64% of their anti-SRP patients, these rates depend heavily on how the studies were conducted, and the true frequency across all patients may be lower ^[3][12]. A commonly reported pattern in these studies is Nonspecific Interstitial Pneumonia (NSIP) ^[3]. Many reported cases of ILD in anti-SRP are mild to moderate, but because severe or progressive cases can occur, clinical assessment is vital ^[13][14].
• Respiratory Muscle Weakness & Aspiration: The severe muscle weakness of IMNM can affect your breathing muscles, leading to shortness of breath or a weak cough ^[8][15]. Weakness in the throat muscles (dysphagia) can also lead to aspiration—accidentally inhaling food or liquid into the lungs—which can cause coughing and pneumonia.

Lung Assessment

Standard evaluation for lung or respiratory muscle issues may include:

• Pulmonary Function Tests (PFTs): Breathing tests measuring lung volume and how well oxygen transfers into your blood (DLCO). To check for respiratory muscle weakness, your doctor might also measure your lung capacity while you are seated versus lying flat (supine FVC), or measure your maximum breathing pressures (MIP/MEP) ^[16][17].
• High-Resolution CT (HRCT): A specialized chest CT scan that provides detailed images of lung tissue. It is not an automatic screening test for everyone due to radiation exposure, but your doctor may order it if you have respiratory symptoms, abnormal PFTs, or specific risk factors for ILD ^[3][16].

By discussing these potential complications with your care team, you can establish an appropriate, individualized monitoring plan that fits your specific situation.