Hien Nguyen, Connie Le, Hanh Nguyen
Internal Medicine Department,
Kaiser Permanente-Mid Atlantic and Medical
College of Virginia School
of Medicine
First Published April 2007
Copyright Priory Lodge Education
Ltd. 2007
DISCUSSION
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.
