I had a fever and lower abdominal pain, but the diagnosis really shocked me.

Senior woman suffering from low back pain. Chiropractic, osteopathy, Physiotherapy. Alternative medicine, pain relief concept.Albina Glisic/Shutterstock

The patient: Maria*, a 61-year-old social worker
The symptoms: Fever and lower abdominal pain
The doctor: Dr. Jean-Luc Reny, head of the Division of General Internal Medicine, Geneva University Hospitals, Switzerland

Maria was exhausted and hadn’t been able to work in weeks. In March 2018, the social worker had developed a mysterious fever that came and went, and her lower abdomen burned 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 she’d have to change all her bedding. Read up on these secret reasons for your back pain.

By mid-April, Maria had lost more than three kilograms 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.

A fever of unknown origin—or FUO—is one of the most onerous diagnostic challenges, says Dr. Jean-Luc Reny. 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 an FUO, the most common being infection, inflammatory disease, and malignancy. Many cases are never solved, and a small fraction of patients even die after developing one, often from cancer.

While recording a detailed history, 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 was thickened with inflammation.

Since Maria had described chest pains, Reny ran an EKG and checked her enzyme levels, but uncovered no leads. On day eight of his work on the case, he ordered a 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 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 be trying to 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, 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 in the United States, the condition 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 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 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 Reny. Next, read about these strange symptoms that could signal a serious disease.

*Biographical details have been changed.