Cutaneous TB. Facial lesions due to conditions associated with TB have been described; these include erythema induratum of Bazin, papulonecrotic tuberculids, and others. M. tuberculosis DNA has been detected in erythema induratum skin lesions by PCR, and erythema nodosum has been attributed to primary TB. Skin involvement may result from exogenous inoculation, spread from an adjacent focus to the overlying skin, or hematogenous spread, often seen in patients with AIDS and tuberculous bacteremia. Any unexplained skin lesion, particularly one with nodular or ulcerative components, may be due to TB, especially in AIDS patients; and biopsy and cultures are warranted.
Skeletal TB. More than 30% of skeletal TB cases involve the spine (tuberculous spondylitis or Pott's disease). The most commonly affected area is the lower thoracic spine, followed by the lumbar, cervical, and sacral areas. The mode of spread to the spine is usually hematogenous, but it also can result from contiguous disease or lymphatic spread from TB pleuritis. In contrast to common bacterial causes of spinal osteomyelitis that initially present as discitis with adjacent vertebral body involvement, TB spondylitis typically begins within the anterior vertebral body. With time, spread to the adjacent disc and vertebra occurs, and vertebral body wedging develops.
Pott's disease is a disease of older age in developed countries and presents with local symptoms of pain and stiffness without systemic manifestations such as fever or weight loss. Initial roentgenograms can be negative. Thus, the diagnosis can be difficult to make, and late complications often appear. These can include paraspinal abscess and sinus tract formation as well as neurological symptoms from spinal instability and cord compression. Paraspinal cold abscesses develop in 50% of patients and can extend along tissue planes and present as masses in remote areas such as the supraclavicular, inguinal, popliteal, or posterior iliac regions.
Bone biopsy rarely yields bacilli but can reveal bone marrow granulomas in about 75% of cases.
The most serious complication is lower extremity paralysis (Pott's paraplegia) from spinal instability and cord compression, inflammatory arachnoiditis, or vasculitis.
A 12-month course of treatment is recommended for Pott's spondylitis. In a review of uncomplicated cases, response rates to systemic chemotherapy and bed rest until pain resolved exceeded 90% (16). Laminectomy does not appear to be dramatically helpful for neurologic complications unless there are advancing defects and severe instability of the spine. In a series of complicated patients, needle aspiration of the paraspinal abscesses along with steroids seemed to be beneficial to successful management (16).
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