Maria remembers the constant exhaustion and her inability to go to work for weeks. In March 2018, the social worker also remembers developing a mysterious fever and her lower abdomen burning with pain. Her family doctor prescribed antibiotics for a suspected urinary tract infection, to no effect. In the night, she would wake up so drenched in sweat that she would have to change all her bedding. She would soon learn her lower abdomen pain was actually low back pain from a rare disease.
By mid-April, Maria lost more than three kilograms (nearly 7 pounds) and, around that time, experienced two episodes of an intense, stabbing chest pain that made her fear for her life. A chest X-ray and abdominal ultrasound came back normal, but after a lab test found Maria’s C-reactive protein count to be high—indicating inflammation somewhere in her body—she was referred to Geneva University Hospitals in Switzerland.
A fever of unknown origin—or FUO—is one of the most onerous diagnostic challenges, says Jean-Luc Reny, MD, PhD, head of the division of general internal medicine, Geneva University Hospitals. By definition, it’s a persistent fever lasting more than three weeks that can’t be explained after a full in-hospital workup. “Solving it is like running a marathon. It’s a matter of training and patience.”
There are over 200 potential causes of FUO, the most common being infection, inflammatory disease, and malignancy, according to a 2015 study in The American Journal of Medicine. Many cases are never solved, and a small fraction of patients even die after developing one, often from cancer.
A medical history review
While recording a detailed history, Dr. Reny learned that Maria had multiple teeth extracted several months earlier, leaving her with sore gums that oozed pus for several days afterwards. “Sinuses and teeth are common sites of chronic infection that can be missed,” he says, but a mouth X-ray showed everything had healed. Maria had also spent time in park areas known to harbor ticks, but she tested negative for Lyme disease.
A scan showed that Maria’s aorta—the large blood vessel that carries oxygenated blood from the heart to the rest of the body—was thickened with inflammation.
Since Maria had described chest pains, Dr. Reny ran an electrocardiogram (EKG) and checked her enzyme levels, but uncovered no leads. On day eight of his work on the case, he ordered a positron emission tomography (PET) scan, which uses radioactive tracers to highlight problems with blood flow or other organ functions. “When you perform this scan because you haven’t found anything yet, it’s frustrating,” says Dr. Reny. Often, though, a PET will uncover a previously undetected inflammatory disease or cancer. And indeed, in this case, it revealed an important clue. (This is what your left side abdominal pain could tell you.)
The scan showed that the wall of Maria’s aorta was thickened with inflammation, from her heart to her abdomen, and into the iliac arteries in her pelvis. With that, Dr. Reny could narrow down the possibilities. One was syphilis, quickly excluded after an antibody test, and another was a type of vasculitis called giant cell arteritis (GCA), or Horton’s disease. According to the National Organization for Rare Disorders, GCA affects 24 in 100,000 people over 50, and more women than men. Left untreated, patients risk losing their vision.
Horton’s disease had already been dismissed in Maria’s case—she reported no relevant symptoms and an artery biopsy had come back negative for it—but Dr. Reny suspected she might have an unusual presentation. (Negative biopsies can happen as the location of the inflammation is not always predictable.)
The most common treatment is prednisone, a corticosteroid. Within 24 hours of being prescribed the medication, Maria’s symptoms improved—confirming Dr. Reny’s diagnosis was correct. “That intense abdominal pain she complained about was actually low back pain,” he says.
Maria’s prescription will gradually be reduced over one to two years. Relapses can occur but are managed by adjusting the medication dose. “For now, she’s back at work—and very thankful,” says Dr. Reny. (Next, read about these strange symptoms that could signal a serious disease.)