Differentials
Lymphoma
SIGNS / SYMPTOMS
There may be no difference in signs and symptoms.
Constitutional symptoms and widespread lymphadenitis are more common in lymphoma.
TB lymphadenitis is most commonly found in the cervical or supraclavicular regions.
INVESTIGATIONS
Chest x-ray may show abnormalities consistent with prior pulmonary TB in about 25% of patients with TB lymphadenitis.
Fine needle aspiration will usually be able to diagnose TB lymphadenitis; if this is nondiagnostic, excisional biopsy must be performed.
Nontuberculous mycobacteria lymphadenitis
SIGNS / SYMPTOMS
There may be no difference in signs and symptoms.
TB lymphadenitis predominates in patients older than 12 years and nontuberculous mycobacteria (NTM) is more common in children under 12 years of age.
TB lymphadenitis predominates in women of Asian background from TB-endemic areas.[1]
INVESTIGATIONS
Chest x-ray may show abnormalities consistent with prior pulmonary TB in about 25% of patients with TB lymphadenitis.
In an adult with acid-fast bacilli or caseating granulomas on fine-needle aspiration, empiric therapy for TB can be started. This is also true if a child has epidemiologic risk factors for TB, pending results of culture.
In a child with presumed NTM, the diagnosis must be proven with culture results.[15][84]
Sarcoidosis
SIGNS / SYMPTOMS
Features of sarcoidosis, such as intrathoracic lymphadenopathy and arthralgias, may be present. A careful review of epidemiologic risk factors for TB can be performed.
INVESTIGATIONS
Tuberculin skin testing will usually be negative with sarcoidosis and chest x-ray may have findings more consistent with TB or sarcoidosis.
Granulomas are noncaseating in sarcoidosis, although it is not diagnostic.
Acid-fast bacilli (AFB) may be seen on fine-needle aspiration in TB lymphadenitis. Culture for AFB is negative in sarcoidosis.
Malignant pleural effusion
SIGNS / SYMPTOMS
There may be no difference in signs and symptoms.
INVESTIGATIONS
CT scan of the chest may show findings more consistent with malignancy (particularly if primary bronchogenic) or with pulmonary TB. A search for a primary in metastatic disease may also diagnose the etiology (e.g., in an effusion due to metastatic breast or ovarian cancer). Cytologic evaluation of the pleural effusion may diagnose a malignant effusion.
Pleural biopsy may reveal granulomas, acid-fast bacilli, or malignant pathology.
Video-assisted thoracic surgery differentiates between an effusion-caused TB and those caused by malignancy.
Cryptococcal meningitis, other fungal central nervous system infections, neurosyphilis
SIGNS / SYMPTOMS
The differential diagnosis of TB meningitis includes disease processes that cause a subacute to chronic meningitis and a lymphocyte-predominant pleocytosis.
Cranial nerve abnormalities are more common in TB.
INVESTIGATIONS
Cerebrospinal fluid (CSF) analysis is the key to making the diagnosis.
Acid-fast bacilli and fungal stain and cultures are usually diagnostic.
Nucleic acid amplification test of CSF may also help in diagnosis.
An elevated adenosine deaminase may support the diagnosis of TB.[85]
Tuberculin skin tests has poor sensitivity with central nervous system TB (approximately 50%).[51]
Inflammatory bowel disease
SIGNS / SYMPTOMS
There may be no difference in signs and symptoms.
The presence of epidemiologic risk factors for TB, a positive tuberculin skin test or chest x-ray findings consistent with TB all support TB as the etiology.
The presence of ascites is more consistent with a diagnosis of TB enteritis.
INVESTIGATIONS
Colonoscopy with biopsy is the best method for diagnosis, with a sensitivity of up to 80%.
The presence of mesenteric lymphadenopathy with central necrosis is suggestive of TB.[81]
Peritoneal carcinomatosis
SIGNS / SYMPTOMS
Epidemiologic risk factors may be present in patients with TB.
INVESTIGATIONS
Cytologic analysis of ascites identifies patients with malignant ascites.
CT scan may identify a primary neoplasm.
Spontaneous bacterial peritonitis
SIGNS / SYMPTOMS
In patients with a history of cirrhosis and epidemiologic risk factors for TB, a high index of suspicion must be maintained for TB peritonitis.
Symptoms are more chronic in those with TB enteritis.
INVESTIGATIONS
Patients with TB peritonitis usually have ascites with a low serum-ascitic albumin gradient and lymphocytes >30%. However, cirrhotics may have peritoneal TB with a low protein and polymorphonuclear leukocytes >250/mL, mimicking spontaneous bacterial peritonitis.
In TB peritonitis, CT scan may reveal abdominal lymphadenopathy.
Differentiating tests include nucleic-acid amplification test, adenosine deaminase, acid-fast bacilli culture, and peritoneal biopsy.
Fever of unknown origin
SIGNS / SYMPTOMS
There may be no difference in signs and symptoms.
The presence of epidemiologic risk factors for TB or coexistence of pulmonary TB may help diagnosis.
INVESTIGATIONS
EPTB, especially disseminated disease, may be responsible for fever of unknown origin. Tuberculin skin tests will usually be negative. Diagnosis may require transbronchial, liver, or bone marrow biopsies.
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