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| Journal of the New Zealand Medical Association,
14-December-2007, Vol 120 No 1267
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Two cases of parotid tuberculosis
Matthew Seeley, David Waterhouse, Subhaschandra Shetty,
Jeremy Gathercole, Chris Seeley
Mycobacterium tuberculosis (TB) infection of the
salivary glands is rare, even in countries with a high prevalence of TB. There
are two distinct forms—a localised form (resulting from infection of
periglandular nodes), and a diffuse form involving the entire gland due to
direct spread from adjacent nodes or primary parenchymal involvement.
Overall, extrapulmonary TB accounts for approximately 20% of
active TB.1 Primary parotid tuberculosis may
present as a slowly growing mass in the region of the parotid gland, resembling
a parotid neoplasm. Clinically, tuberculous salivary gland disease and a
neoplasm cannot be distinguished.
It is important to differentiate the two forms, as salivary
gland TB can be treated medically, thus avoiding potential surgical
complications.
Case reportsA 45-year-old Filipino woman, who had immigrated to New
Zealand 17 years previously, presented with a left parotid swelling of 1
year’s duration. She had recently visited her brother in the Phillipines,
who was subsequently diagnosed with TB. She underwent left superficial
parotidectomy, after 5 unsuccessful attempts to obtain cytology via fine needle
aspiration (FNAC). Postoperative histology confirmed granulomatous parotid
disease.
A 42-year-old Filipino man, who had been living in New
Zealand for 1 year, presented with a 1-month history of painless right
pre-auricular swelling. CT showed a homogenously enhancing parotid lesion and
apical pulmonary fibrosis bilaterally. His immigration chest film 1 year before
was normal, and Mantoux tests were repeatedly negative. FNAC suggested a
granulomatous lesion, confirmed by positive culture of Mycobacterium
tuberculosis. Polymerase chain reaction (PCR) was negative.
Both patients were diagnosed with non-resistant TB, and were
treated with the 2RHZ/4RH regimen (as per the
New Zealand Ministry of Health guidelines).2 R,
H and Z signify rifampicin, isoniazid, and pyrazinamide respectively—the
treatment course involves 4 months of all three drugs, followed by a further 2
months of rifampicin and isoniazid.
Neither patient encountered any serious adverse reactions
while on treatment and both are now cured.
DiscussionTB parotitis usually has an insidious clinical course, and
may exist for up to 15 years without causing a systemic inflammatory response in
a host. However, when host immunity is attenuated, the affected site will
rapidly enlarge. TB parotitis occurs equally among men and women, and typically
affects patients between 30 and 50 years of age.
There are no statistics available in New Zealand reporting
the prevalence of parotid tuberculosis, but ‘other’ tuberculous
disease (including salivary gland involvement) makes up 17% of extrapulmonary
disease with 147 cases reported in New Zealand between 1995 and
2001.2
Tuberculosis cases in foreign-born individuals may be the
result of reactivation, reinfection, or undiagnosed TB during
immigration.3 A normal chest radiograph and
negative Mantoux test (the standard screening methods for immigrants to New
Zealand) do not exclude TB, particularly extrapulmonary cases.
TB parotitis can have a variety of appearances on computed
tomography (CT) scanning, and may mimic inflammatory and neoplastic
conditions.
Traditionally, tuberculous salivary gland disease has been
diagnosed with a combination of acid-fast bacilli (AFB) staining, culture, and
FNAC, and histology in some cases. AFB staining requires the presence of many
bacteria to be detected histopathologically, and culture can take up to 6 weeks
to return a result.
Cytology may require multiple samples. PCR is a more recent
diagnostic technique; it is very helpful in rapid detection of drug-resistant
mutations. However, sensitivity is limited in extrapulmonary TB due to low
bacterial numbers.4
There may also be a role in future for interferon-γ
T-cell assays, especially in low-incidence settings like New
Zealand.4 The test uses an enzyme-linked assay
to detect T-cells specific for the M. tuberculosis proteins ESAT-6 and
CFP-10, which are absent in the Bacillus Calmette-Guerin (BCG) vaccine and in
most environmental mycobacteria. The test is not confounded by BCG immunisation
and has better correlation with TB exposure than Mantoux testing, suggesting a
role in settings where the bacterial burden is
low.5
In light of the drawbacks of each method, they are usually
used in combination for preoperative diagnosis. This enables the condition to be
treated with anti-tuberculous chemotherapy, avoiding surgical resection and
associated morbidity.
In summary, we emphasise the importance of early diagnosis
of tuberculous salivary gland disease, to avoid surgery and commence effective
anti-TB chemotherapy.
Though rare, TB should be considered in the differential
diagnosis of a diffuse swelling of the parotid, particularly in immigrant
populations.
Author information: Matthew Seeley, David
Waterhouse, Subhaschandra Shetty, Jeremy Gathercole, Chris Seeley;
Otorhinolaryngology – Head and Neck Surgery Department, Whangarei
Hospital, Whangarei, Northland
Acknowledgement: The Surgical Services
Department at Whangarei Hospital supplied funding for this project.
Correspondence: Matthew Seeley, PO Box
10175, Te Mai, Whangarei, Northland, New Zealand. Email: matthew.seely@gmail.com
References:
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