BY MARK GRANT, DO
A 31-year-old man presented to the emergency department with dyspnea, fever, cough, and weakness for two weeks. He had recently seen his internist, and was diagnosed with a viral infection. He was seen again at an urgent care center a few days before his ED presentation, and was diagnosed with bronchitis and an ear infection and placed on an antibiotic.
The patient said in the ED that he was not improving, and was now experiencing back pain, shortness of breath, and occasional fevers and sweats. The patient stated he had sharp chest pain at times and was coughing up clear sputum more often over the previous few days, but had no hemoptysis, orthopnea, abdominal pain, vomiting, diarrhea, dysuria, hematuria, headache, neurologic complaints, or rashes. Physical examination revealed no otitis media or pain to palpation of the joints or spine. His lungs were clear to auscultation.
The patient in the past two weeks had driven from Texas to Michigan. The patient had no history of pulmonary embolism or DVT, and had no significant past medical history. He was born in India, moved here as a child, and was up to date with immunizations. The patient and his family have no history of tuberculosis. His initial vital signs were blood pressure of 112/72 mm Hg, temperature of 98.7°F, pulse ox of 99% on room air, and respiratory rate of 18 bpm.
An IV was established, and the patient was hydrated and labs obtained. The patient's CBC, basic metabolic panel, and urinalysis were unremarkable. An influenza swab was performed and returned negative. The sedimentation rate was 50 mm/hr and the C-reactive protein was 73 mg/LD. The D-dimer was positive at 525 ng/ml.
A chest x-ray interpreted by radiology is negative for an acute process. A chest CT is obtained because of the patient's recent travel history, dyspnea, and positive D-dimer. The CT thorax images show no pulmonary embolism, but a lytic and sclerotic lesion involving the T7 vertebrae and thickening of the soft tissue surrounding the perivertebral tissue of T7. The CT of the thorax also shows mild right hilar lymphadenopathy.
CT and MRI images showing Pott disease.
This patient has Pott disease, the name given to tuberculous spondylitis by British surgeon Percivall Pott (1714-1788). Pott disease results from hematogenous spread of tuberculosis from other sites, most often the lungs, to the upper and lower vertebrae. Most commonly, however, spread of this acid-fast bacilli Mycobacterium is to the thoracic vertebrae, as seen in this patient. (Neurosurg Rev 2001;24:8.) The infection then spreads from adjacent vertebrae through the intervertebral discs, and destroys the disc and vertebrae, which can lead to disc collapse and spinal cord damage. (Spine 2007;32:E130.) Bone and soft-tissue tuberculosis accounts for approximately 10-15 percent of extrapulmonary tuberculosis cases and between one and two percent of total cases. Tuberculous spondylitis is the most common manifestation of musculoskeletal tuberculosis, accounting for approximately 40-50 percent of cases. (N Am J Med Sci 2013;5:404.)
Patients with Pott disease typically present with back pain. The average duration of nonspecific back pain before diagnosis is around four months, and can be accompanied by fever, night sweats, cough, and weight loss, which can clue a clinician into the diagnosis. (Postgrad Med J 2006;82:46.)
The sedimentation rate and the C-reactive protein are uniformly elevated while the CBC, basic metabolic panel, and other tests are usually normal. The tuberculin skin test (PPD) is positive in 85-95 percent of patients with Pott disease who are not HIV-positive. Bone tissue or abscess samples through CT-guided biopsy for acid-fast bacilli stain and culture is anywhere from 50 percent to 83 percent sensitive. (S Afr Med J 2013;104:29.) This patient underwent interventional CT-guided biopsy and grew out the organism Mycobacterium chelonae.
Radiologic findings occur late in the diagnosis of Pott disease, and they suggest the diagnosis on plain x-ray as osteoporotic-appearing vertebral end plates, intervertebral discs that are shrunken or destroyed, bony lytic lesions, and hilar lymphadenopathy on PA and lateral chest x-ray. (Orthopedics 1998;21:1213.) CT scanning reveals much more detail of the bony lytic lesions, disc collapse, and classic calcification abscess lesions of tuberculosis. (Radiol Clin North Am 1995;33:787.)
Magnetic resonance imaging is the standard for evaluating disk-space infection and osteomyelitis of the spine, and it is most effective for demonstrating the extension of disease into soft tissues and the spread of tuberculous debris under the anterior and posterior longitudinal ligaments. MRI is also effective in demonstrating abscess formation as well as neuronal involvement. (Eur J Radiol 2005;55:193.) The MRI images in this patient confirm spread of the infection from T6 through T8 with discitis, osteolytic lesions, and epidural abscess but no cord edema.
Once the diagnosis of Pott disease is established, treatment options vary, and is typically individualized for each patient (J Int Med Res 2013;41:1395), including a combination of chemotherapy and surgical management with consideration of the patient's medical stability and neurologic symptomatology.
A four-drug regimen should be used empirically to treat Pott disease, according to 2003 recommendations from the Centers for Disease Control and Prevention, the Infectious Diseases Society of America, and the American Thoracic Society. Isoniazid and rifampin should be administered during the whole course of therapy. (Am J Respir Crit Care Med 2003;167:603.) Additional drugs are administered during the first two months of therapy, generally chosen from among the first-line drugs, which include pyrazinamide, ethambutol, and streptomycin. The use of second-line drugs is indicated in cases of drug resistance. (Int Orthop 2012;36:277.) Studies performed by the British Medical Research Council indicate that tuberculous spondylitis of the thoracolumbar spine should be treated with combination chemotherapy for six to 12 months. (J Bone Joint Surg Br 1993;75:240.)
Indications for surgical treatment of Pott disease generally include neurologic deficits, unstable spinal deformity, a large paraspinal abscess, intractable pain, and continued bony spread and destruction. (J Bone Joint Surg Am 1996;78:288.) Vertebral damage is considered severe if greater than 50 percent of the vertebral body is collapsed or destroyed.
Pott disease is the most severe form of musculoskeletal tuberculosis because of the bony destruction, deformity, and subsequent neurologic disability (paraplegia) that can occur. This case highlights the importance of keeping a wide differential diagnosis for patients with multiple visits with no clear-cut diagnosis and the importance of addressing any potential lab abnormalities. The busy times in the emergency department should never detour the clinician from performing a good history and physical examination.
Dr. Grant is an assistant clinical professor of emergency medicine at Michigan State University/College of Osteopathic Medicine/College of Human Medicine.