When does a fever become life-threatening? Abu Dhabi doctors reveal rare diagnosis

Dubai: Most fevers come and go within a few days. But what happens when the temperature keeps rising, tests keep coming back negative, and no one can explain why?

That was the frightening reality for a 34-year-old Abu Dhabi resident whose persistent high-grade fever lasted for more than two weeks, turning what initially seemed like a common illness into a medical mystery.

The man had always enjoyed robust health. Yet despite multiple hospital visits and investigations, including blood cultures and standard infection screening tests, doctors could not identify the cause of his worsening condition.

As the fever continued, other symptoms emerged. Severe joint pain made movement difficult. Extreme fatigue left him struggling with daily activities. Tests also showed significant inflammation and liver involvement, raising concerns among doctors that something far more serious was unfolding.

Although he appeared clinically stable, the persistence and severity of his symptoms prompted specialists at Burjeel Hospital in Abu Dhabi, to look beyond the usual causes of prolonged fever. What they eventually discovered was a rare autoimmune disorder that affects only one to four people per million people worldwide.

After an extensive work-up, doctors have diagnosed the patient with Adult-Onset Still’s Disease (AOSD), a rare inflammatory condition that can be difficult to identify even for experienced physicians.

Dr. Niyas Khalid, specialist in internal medicine at Burjeel Hospital, has noted that the disease often hides behind symptoms that resemble many other illnesses.

“It mimics many life-threatening diseases such as severe infections, autoimmune disorders, liver disease, and even cancer. It’s often under-recognised, particularly in regions where fever is commonly attributed to infectious causes,” explained Khalid, who treated the patient along with Dr. Abdul Hakeem Muhammed, specialist in internal medicine.

One challenge was that the patient did not have a rash, a symptom frequently associated with the disease in medical textbooks. However, Khalid has bared that rashes can be absent or difficult to detect, particularly in people with darker complexions.

Instead, doctors have relied on a combination of other findings. The patient had prolonged fever, severe inflammation, liver involvement, and remarkably high ferritin levels. At the same time, every infectious and autoimmune test returned negative.

“The extraordinarily elevated ferritin, a marker of inflammation, acted as a critical diagnostic signal. When these features came together, along with high-grade fever spiking every day at regular intervals, AOSD became the most plausible explanation, although it is extremely rare.”

While fever is usually the body's natural response to infection, doctors have highlighted that persistent fever accompanied by severe inflammation can sometimes signal a more serious underlying condition.

In AOSD, the immune system becomes overactive and attacks the body's own tissues, triggering widespread inflammation. If not recognised and treated in time, the disease can progress to chronic inflammatory arthritis, organ damage, liver failure, or a potentially fatal immune storm known as macrophage activation syndrome.

For the Abu Dhabi resident, the physical and emotional toll had already become overwhelming. 

“During those days, I shivered from fever and struggled to get up from bed, lift my hands, and move my body. There was no appetite because of throat pain. Despite taking medicine, my fever recurred, draining me emotionally. I prayed to God to give my routine life back,” recalled the patient.

Once doctors have suspected AOSD, they immediately started high-dose corticosteroid therapy, the standard treatment used to suppress the abnormal immune response driving the disease. 

“Within 24 hours, the fever subsided. Within 48 hours, the patient felt significantly better, with improvement in joint pain and energy levels. Laboratory markers improved in parallel,” shared Khalid.

After the initial high-dose treatment, the medication has been gradually tapered over several weeks to allow a safe recovery while keeping inflammation under control. For the patient, the turnaround has felt almost unbelievable after weeks of uncertainty.

“I am so happy that I can move my body without support for the first time after a while. Everyone in the hospital gave me hope whenever I doubted, got frustrated, and questioned myself,” said the patient.

Although the patient has recovered remarkably well, his journey is not entirely over. Doctors have pointed out that AOSD can recur in some patients, making ongoing follow-up essential.

His case has also served as a reminder that when a fever persists for weeks without an obvious explanation, it may be a warning sign that something more complex is happening inside the body. 

Meanwhile, he will continue regular monitoring with internal medicine and rheumatology specialists to watch for signs of relapse and ensure long-term stability.