Can Fever Be a Symptom of Antisynthetase Syndrome?

Yes, fever is a recognized symptom of antisynthetase syndrome ^[1][2]. While it is not always present, unexplained fevers can occur, especially when the disease is active or flaring up (a flare means worsening autoimmune disease activity) ^[3]. Because antisynthetase syndrome involves systemic inflammation, autoimmune activity can release signals that raise your body temperature ^[3]. However, because the medications used to treat the condition suppress the immune system, any new fever must be carefully evaluated by a doctor to rule out an infection ^[4][5].

Important: What to do if you develop a fever

• Do not wait: If you are on immunosuppressive medications, an infection can be a medical emergency. Many care centers advise calling the clinic same-day for a temperature of 100.4°F (38.0°C) or higher, but always follow the specific threshold your doctor has given you.
• Do not change your medications: Never stop, hold, or increase your prednisone or other immunosuppressants without direct instructions from your doctor.
• Seek emergency care immediately if a fever is accompanied by severe shortness of breath, rapidly dropping oxygen levels, blue lips, chest pain, inability to keep fluids down, or confusion ^[6][7].

Fever as a Symptom of Antisynthetase Syndrome

Fever is considered one of the potential clinical features of antisynthetase syndrome ^[1][2]. The likelihood of experiencing a fever varies widely depending on the individual. Different studies have reported fever in roughly 17% to 61% of patients at the time of diagnosis, though these numbers depend heavily on the specific patient groups and time periods studied ^[8][9][4].

For some people, recurrent attacks of non-infectious fever can occur ^[3]. These disease-related fevers are sometimes tied to active inflammation or a flare-up of the condition. In some study cohorts, fever has been observed alongside more severe organ involvement, such as rapidly progressive interstitial lung disease (RP-ILD)—a rapid worsening of interstitial lung disease and respiratory function ^[3][10]. However, a fever alone does not mean you have RP-ILD, nor does it reliably predict how severe your flare is. Rapidly worsening breathlessness or cough—not fever alone—requires urgent evaluation.

Fevers might also occur when corticosteroid medications (like prednisone) are being tapered down ^[11][12]. While this could suggest that underlying disease activity is returning, a fever during a taper is non-specific. It could just as easily be an infection or a medication reaction, which is why you must consult your doctor rather than assuming it is a flare.

The Challenge: Disease Flare vs. Infection

The biggest challenge when a patient with antisynthetase syndrome develops a fever is determining the cause ^[4][5]. It could be the disease itself, but it could also be an infection, a medication reaction, or another unrelated illness.

Because the cornerstone of treatment for antisynthetase syndrome involves immunosuppressive medications (drugs that reduce the immune system’s activity), patients are at a higher risk of developing infections ^[4][5]. In one specific study cohort, 63% of patients experienced an infection during the course of their illness, though your individual risk depends heavily on your specific drugs, doses, age, and other health conditions ^[4]. These can include common infections like pneumonia, or opportunistic infections (infections that occur more often or are more severe in people with weakened immune systems) ^[5][12].

It can be very difficult to tell the difference between a disease flare and an infection because both can cause fever and worsening lung symptoms, such as shortness of breath or cough ^[10][6][5]. Furthermore, an infection and a disease flare can happen at the exact same time ^[5][13].

Crucial note: Because immunosuppressive medications like prednisone can blunt your body’s typical warning signs, you can have a serious infection without a high fever or with completely normal inflammatory blood markers. Never assume that the absence of a fever makes a worsening cough, breathlessness, or low oxygen safe to ignore.

How Doctors Investigate a New Fever

Because it is dangerous to assume a fever is just a disease flare, doctors will typically perform a thorough evaluation ^[5][14]. If an infection is missed and the doctor increases immunosuppressive medications to treat a suspected flare, the infection could rapidly worsen ^[5].

Having a fever can be stressful, but needing tests does not mean a dangerous complication is definitely present—clinicians often cannot distinguish a flare from an infection based on symptoms alone. Your evaluation will usually begin with a physical exam, checking your vital signs and oxygen, and targeted tests, which may include:

• Blood, urine, and viral tests: They will check for markers of inflammation and run cultures to look for specific infections. While some markers, like procalcitonin, can sometimes help provide evidence of a bacterial infection, no single test is perfect ^[15][16].
• Chest imaging: If you have severe respiratory symptoms, a high-resolution CT scan of the chest may be selected to identify signs of lung inflammation or infection ^[17][5]. However, the imaging patterns for both can overlap ^[17][5].
• Bronchoalveolar lavage (BAL): If you have severe lung symptoms and less invasive tests cannot provide a clear answer, a doctor may consider a bronchoscopy. In this procedure, a thin tube is passed into the lungs to collect fluid for testing. This is an invasive procedure with risks, so it is only used to help evaluate for hidden infections when the expected benefits outweigh those risks ^[18][13].