Tuberculosis (TB) is caused by a bacterium called Mycobacteria tuberculosis. Although TB primarily affects the lungs, it sometimes spreads to other body areas, producing extrapulmonary TB.
In about 20 to 30 percent of people with extrapulmonary TB, the infection occurs in one or more bones, according to an August 2010 article in the “International Journal of Infectious Diseases.” Although TB can involve any bone, the spinal bones -- called vertebrae -- are most commonly affected, notes an article in the November 2005 issue of “American Family Physician.” TB in bones can produce pain, as well as other symptoms.
Pain is the most common symptom of TB in bone. It is typically a constant, aching sensation, which can be mild, especially early on. The pain is centered around the bone containing the infection. TB of the spine, for example, usually affects the vertebrae in the middle of the back, called the thoracic spine. Therefore, spinal TB -- also known as Pott disease -- usually produces middle back pain. Stiffness may accompany the pain with spinal TB.
As spinal TB worsens, it can spread from one vertebra to the next, weakening the bones and destroying the cushioning disc between them. When severe, the vertebrae will collapse. This may pinch, or compress, nerves entering or exiting the spinal cord or even the spinal cord itself.
Nerve compression typically produces pain, numbness, tingling or weakness. The location of these symptoms depends on which nerve is pinched. Weakness or paralysis of both legs and loss of bowel or bladder control may occur if the spinal cord is compressed. Leg paralysis eventually occurs in up to 50 percent of people with untreated Pott disease, according to Medscape.
TB in bones outside the spine may also compress adjacent nerves. If TB involves the wrist bones, for example, it may compress the median nerve, producing symptoms of carpal tunnel syndrome.
If spinal TB destroys vertebrae and discs, the spine can lose its normal shape. When the thoracic spine is affected, the front part of the vertebrae is usually more severely destroyed than the back part. This tends to produce an outward pointing bump in the spine. This bump, called a gibbus, may not be obvious by simply looking at the back, but it will be clearly visible on an x-ray.
Other Localized Symptoms
When TB in bone is left untreated, the infection can travel into the surrounding tissues. This can produce an abscess in the area, characterized by swelling and more severe pain. With spinal TB, abscesses may develop in the epidural space surrounding the spinal cord. They are another cause of nerve or spinal cord compression in Pott disease.
When TB affects bones near joints, the infection may travel into the joint, producing TB arthritis. The hips and knees are the most commonly involved joints. Arthritis due to TB produces joint pain, stiffness and swelling.
Patients with bone TB may or may not have generalized symptoms of TB, such as fever, fatigue, night sweats or unexplained weight loss. Approximately one-third of people with spinal TB have generalized symptoms, according to a June 2013 article published in "European Spine Journal."
Although people with bone TB may have evidence of lung TB on chest x-ray, the infection is usually not active there. This means that most people with bone TB have no lung symptoms and are not contagious.
See your doctor if you have persistent or worsening pain in your back or other bones. Your doctor may recommend x-rays or a CT or MRI scan to help determine the diagnosis. Obtaining a biopsy sample of the bone lesion or surrounding area of infection may also be necessary. If you have bone TB, you will usually require multiple antibiotics for months.
Seek immediate medical care if you notice any symptoms suggesting an abscess, or nerve or spinal cord compression. Emergency medical care is needed for these conditions, which may involve surgery.
Reviewed and revised by Mary D. Daley, M.D.