Journal of the New Zealand Medical Association, 14-December-2007, Vol 120 No 1267
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.
A 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.
TB 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: firstname.lastname@example.org
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