Ho-hum, I thought. Another patient with a swollen lymph node in her neck.

I see these day in and day out, and they are seldom of concern. Most people worry it's a sign of cancer. That's possible. But malignant nodes are usually stony hard, fixed to the skin or underlying structures, and generally not painful. Lymph nodes mainly act as filtering stations for the immune system to protect us from microbial invaders, so the ones in the neck usually enlarge and get sore during upper respiratory infections.

Indeed, this 45-year-old woman had had a cold about three weeks before. Those symptoms were all gone, but she still had a lump under the left side of her jaw. It was a little sore, it moved freely, and there was nothing else apparent on physical exam, so I reassured her it probably wasn't anything to worry about, and to come back in a month if it was still there.

A month later, it still was. It was a little larger, and now it seemed stuck to the underside of her jawbone. My "Spidey sense" went off as I ordered a CT scan and referred her to an ear, nose, and throat specialist (ENT) for a biopsy.

The CT confirmed the lump was indeed a lymph node, but there was also another one below it that was a little bigger - and a lot more worrisome. So it was off to the OR for an excisional biopsy.

The ENT took out the bigger of the two lumps during surgery, and I held my breath waiting for the pathology report. When it arrived, I exhaled: nothing but granulomas, a benign finding that generally indicates the presence of localized tissue inflammation.

I lost track of the patient for a while, but the ENT didn't. He kept wondering about that first lymph node, and why it wasn't going away. He tried some antibiotics, then some different ones. But the node didn't change. Finally, he sent a small sample of tissue for more testing.

Three weeks later, he called me.

Solution:

Our patient had tuberculosis.

In retrospect, there was a clue in the pathology report. Two kinds of granulomas were described: caseating and non-caseating. "Caseating" refers to a crumbly appearance under the microscope that looks like cheese, caseus in Latin. Caseating granulomas are the pathologic hallmark of TB.

TB is still around. The bacterium that causes it, mycobacterium tuberculosis, is a strange organism: extremely slow-growing and requiring special nutrient media, getting it to grow in a petri dish can be very difficult. It's important to correctly diagnose it, though, because TB is contagious and notoriously difficult to treat.

Most of the time, TB is diagnosed with a skin test that identifies an immune reaction to the organism. Known as a Mantoux text, it involves injecting a small amount of purified protein derivative (PPD) under the skin and then inspecting the area 48 to 72 hours later. More recently, blood tests have been developed that don't require a second visit for the reading. None of these are definitive, though, and, when positive, require further testing. Interestingly, this patient did not have a positive PPD when tested for her residency green card five years ago, and her TB blood test was negative now.

TB is an important public health issue because of the danger of spreading it. The vast majority of TB cases are so-called pulmonary tuberculosis, a lung infection that classically presents with fevers, night sweats, weight loss, and coughing up blood. Our patient had none of those symptoms, and her chest X-ray was clear. Nevertheless, the local health department took charge of her treatment because the positive culture technically meant she had active TB, even though she was not contagious. She can continue to work and do as she pleases, with no restrictions on her activity.

Treatment consists of four different antibiotics taken every day for two months, then the same four antibiotics twice a week for four months after that. The very long treatment period is required because of how slowly the bacterium grows. Multiple drugs are necessary to prevent resistance, an enormous problem globally. Multidrug-resistant tuberculosis is especially problematic for patients infected with HIV and others with impaired immune systems.

Although we're still not sure how our patient became infected, her prognosis for a complete cure is excellent.

Lucy Hornstein is a family physician in Phoenixville. She blogs at http://dinosaurmusings.wordpress.com.