Dr Astrid wrote the following case report which was published in Medical Forum Magazine in 2015. This article is quite technical, and was written primarily for an audience of doctors. It includes data on rates of tuberculosis in Western Australia.
Presentation:
A 22 year old from Myanmar presents with bilateral neck swellings increasing in size over three months. He denies fevers, sore throat, a cough, haemoptysis, weight loss or a recent upper respiratory tract infection. He feels tired. On examination, there is a 5×7 cm warm, tender right sided cervical swelling and smaller enlarged lymph nodes are present on the left posterior to the sternomastoid. The oropharynx is normal and chest auscultation is clear. What is the differential diagnosis? What are the most relevant investigations?
Discussion:
Bacterial (streptococcal pharyngitis, bartonella infection) or viral lymphadenitis (infectious mononucleosis, rubella) are the most likely aetiologies with lymphoma or thyroid malignancy the most common non-infective causes. However, active tuberculosis is the most common cause for neck swellings in countries where TB is endemic, as is the case in Mynamar, where this young man comes from. Epidemiologically, his clinical presentation warrants a change in the differential diagnosis with active tuberculosis at the top of the list.
Active tuberculosis cases in WA mirror the prevalence in the rest of Australia with 5.0/100,000 cases each year. WA had 142 cases of active TB in 2014 (see table 1). Certain groups within our population have much higher rates of TB (overseas born, indigenous Australians) and TB is an important differential diagnosis in the presentation of an unexplained cough > 3 weeks especially in the presence of sweats and fevers.
Thinking of active TB is the first step in the diagnosis. The majority of cases (75%) are pulmonary and can present with a cough, haemoptysis and cachexia but often are aymptomatic. A high index of suspicion is required to make the diagnosis (e.g. screening CXR for VISA application). The second most common presentation is TB lymphadenitis often with a painless, firm swelling that increases in size over time with or without systemic symptoms.
Tuberculosis is a microbiological diagnosis and sputum AFB (acid fast bacilli) examination is highly sensitive. In this case, cervical lymph node FNA showed AFB and a GeneXpert1 revealed a positive Mycobacterium tuberculosis (MTB) PCR without rifampicin resistance. Subsequent cultures grew a fully susceptible MTB isolate. The patient had a CXR (fig. 1) and sputum AFBs were smear negative but culture positive. CT scan does not add sensitivity to the diagnosis and is not required, except in miliary TB cases.
Treatment is effective and curative in >95% of cases and it is important that cases are managed by experienced TB physicians. The WA TB Control Program located at the Anita Clayton Centre manages active TB cases in WA and TB physicians are available for advice on 08 9222 8500. The service is provided free of charge to all referred individuals.
1. The GeneXpert MTB/RIF is a cartridge-based, automated diagnostic test that can identify Mycobacterium tuberculosis (MTB) DNA and resistance to rifampicin (RIF) by nucleic acid amplification technique(NAAT).
Table 1. Western Australia Tuberculosis Data January-December 2014
|
0-14 years |
15-49 yrs |
50-64yrs |
65+yrs |
Total |
Total% |
|
|
Sex |
||||||
|
Male |
5 |
40 |
12 |
17 |
74 |
52% |
|
Female |
4 |
49 |
8 |
7 |
68 |
48% |
|
Total |
9 |
89 |
20 |
24 |
142 |
100% |
|
Country of birth/ Indigenous status |
||||||
|
Australia born – non Indigenous |
4 |
3 |
3 |
4 |
14 |
10% |
|
Australian born – Indigenous |
0 |
0 |
1 |
0 |
1 |
1% |
|
Overseas born |
5 |
85 |
15 |
20 |
125 |
88% |
|
Unknown |
0 |
1 |
1 |
0 |
2 |
1% |
|
Total |
9 |
89 |
20 |
24 |
142 |
100% |
|
Case classification |
||||||
|
New |
9 |
84 |
18 |
22 |
133 |
94% |
|
Relapse following full or partial treatment |
0 |
4 |
1 |
1 |
6 |
4% |
|
Treatment after failure |
0 |
0 |
0 |
0 |
0 |
0% |
|
Unknown |
0 |
1 |
1 |
1 |
3 |
2% |
|
Total |
9 |
89 |
20 |
24 |
142 |
100% |
|
Clinical presentation |
||||||
|
Pulmonary only |
4 |
39 |
12 |
12 |
67 |
47% |
|
Pulmonary plus other sites |
2 |
9 |
2 |
4 |
17 |
12% |
|
Extrapulmonary |
3 |
41 |
5 |
7 |
56 |
39% |
|
Unknown |
0 |
0 |
1 |
1 |
2 |
1% |
|
Total |
9 |
89 |
20 |
24 |
142 |
100% |
|
Laboratory results |
||||||
|
Sputum smear and culture positive |
1 |
12 |
5 |
9 |
27 |
19% |
|
Sputum culture positive (smear negative) |
0 |
18 |
4 |
2 |
24 |
17% |
|
Other culture positive |
0 |
40 |
6 |
5 |
51 |
38% |
|
Nucleic acid testing(a) |
0 |
4 |
1 |
1 |
6 |
4% |
|
Unproven(b) |
5 |
15 |
4 |
7 |
31 |
22% |
|
Total |
6 |
89 |
20 |
24 |
139 |
100% |
*Data provided by the WA TB Control Program.
a) Cases with a positive nucleic acid test result without a positive culture result.
b) Cases with no positive culture result or no positive nucleic acid test result.