Hien Nguyen, Connie Le, Hanh NguyenInternal Medicine Department, Kaiser Permanente-Mid Atlantic and
First Published April 2007
Copyright Priory Lodge Education Ltd. 2007
Mycobacterium tuberculosis is a multi-systemic infection. A resurgence of cases of M tuberculosis infection and extrapulmonary involvement has occurred in parallel with the HIV epidemic. Lymphadenopathy is the most frequent extrapulmonary manifestation and pleural tuberculosis occurs in 5% of tuberculosis.
Clues that suggest possible extrapulmonary tuberculosis include chronic lymphadenopathy, pleural effusion and thickening , HIV infection, monoarticular joint inflammation with negative bacterial cultures, immigration from endemic regions, and osteomyelitis of the thoracic vertebra.
M tuberculosis is rarely associated with cutaneous or osteoarticular infection. This case report illustrates an unusual case of tuberculosis presenting with concurrent cutaneous abscess. We postulate that the soft tissue abscess of the abdominal wall occurred by direct extension from the underlying left hepatic abscess. The final diagnosis was confounded by radiographic findings that were more suggestive of a neoplastic process.
Overall cutaneous tuberculosis accounts for .14% of all cases of tuberculosis. Cutaneous tuberculosis can arise from direct inocculation from an exogenous source, contiguous, or hematogenous spread from an endogenous focus. Most often, cutaneous tuberculosis arises from hematogenous dissemination of tubercle bacilli from the lung. Clinical appearances of cutaneous tuberculosis may include papulovesicles, pustules, macules, or nodules. Although the diagnosis of cutaneous tuberculosis may be confirmed by acid fast staining from cutaneous biopsy, results are often negative because skin lesions are typically paucibacillary. Polymerase chain reaction (PCR) for detection of M tuberculosis improves the probability of diagnosis, especially in cases where there is high clinical suspicion.
The classifications of cutaneous tuberculosis include lupus vulgaris, miliary tuberculosis, scrofuloderma, and tuberculous gumma. Our patient had the scrofuloderma type. This skin lesion occurs by direct extension into the skin from an underlying tuberculous focus, which was the left liver in our case. The initial lesion is a firm subcutaneous area that not yet suppurates into an ulcer, fistula, sinus or abscess. Ulcers tend to have blue, undermined edges with soft granulation. Other common sites for scrofuloderma are the neck, supraclavicular fossae, and groin. In contrast, the classic morphologic appearance of lupus vulgaris is a red-brown plaque with “apple jelly” color on diascopy. Common sites of infection are the head and neck, arms, legs, and trunk. Tuberculous gumma appear as single or multiple cold subcutaneous nodules, or abscesses with sinuses and ulcers. Miliary tuberculosis is characterized by discrete pinhead blue to red macules or papules with a predilection for the trunk, thighs, buttocks, and genitalia.
Osteoarticular tuberculosis is a rare manifestation of extrapulmonary tuberculosis. Foot involvement accounts for less than 10% of cases of osteoarticular tuberculosis. Osteoarticular tuberculosis arises from hematogenous, lymphatic, or direct contiguous spread from visceral tuberculosis. Most commonly, osteoarticular tuberculosis originates from a foci of bacilli lodged hematogenously during primary mycobacteremia. Osteoarticular infection may also occur from lymphatic drainage from paraortic lymph nodes.
The symptoms of osteoarticular tuberculosis are nonspecific and often indolent, including pain, joint swelling, or reduced range of motion. Subsequently, there may be delays in diagnosis and therapy, with progression to bone and joint destruction and deformities. A high index of suspicion for osteoarticular tuberculosis should be maintained in populations at risk including immigrants and immunosupressed patients. Our patient never complained of foot pain, which examplifies the difficulty in diagnosing early stages of osteoarticular infection.
Radiographic signs of osteoarticular tuberculosis are nonspecific as well, including soft tissue swelling, osteopenia, joint space narrowing, and subchondral erosions. Nonspecific changes such as radiolucency or sclerotic changes such as observed in our patient, may mimic signs of malignancy. Computerized tomography (CT), magnetic resonance imaging (MRI), or ultrasound may facilitate diagnosis. Osteoarticular infection may be confirmed by AFB staining or isolation of M tuberculosis from bone biopsy.
In conclusion, cutaneous tuberculosis should be included in the differential diagnosis of patients with cutaneous abscesses or musculoskeletal complaints, particularly in high risk populations such as immigrants from endemic regions and immunosupressed patients. Further, this case is a reminder to clinicians that extrapulmonary manifestations may serve as the initial clues to the diagnosis of M tuberculosis infection. Antibiotic therapy and duration for cutaneous and skeletal tuberculosis are the same as for pulmonary tuberculosis.