Investigations
1st investigations to order
FBC
Test
Leukocytosis present in most cases.
Result
WBC count >10x10⁹/litre may be reported
anti-streptolysin-O titre
Test
Indicates streptococcal infection. Ideally checked at first visit, and repeated 2 to 4 weeks later.
Result
elevated in streptococcal infection
chest x-ray
Test
Bilateral hilar adenopathy indicates sarcoidosis, whereas unilateral hilar adenopathy indicates tuberculosis, histoplasmosis, coccidioidomycosis, and brucellosis.
Result
abnormal
tuberculin skin test, interferon gamma release assay
Test
Indicates tuberculosis.
Result
positive in tuberculosis
Investigations to consider
serum ACE level
Test
60% of patients with sarcoidosis have high ACE levels.
Result
elevated in sarcoidosis
skin lesion biopsy
Test
In the absence of a classic sarcoidosis presentation, diagnosis may be confirmed with biopsy of a lesion other than an EN lesion; biopsies of the EN lesions in sarcoidosis will be typical of EN, not of sarcoidosis.
Result
may exclude EN and confirm sarcoid lesion
coccidioidin skin test
Test
Seen with adenopathy on chest x-ray in patients with coccidioidomycosis infection.
Result
positive in coccidioidomycosis infection
histoplasmin skin test
Test
Seen with chest x-ray findings of adenopathy in patients with histoplasmosis infection.
Result
positive in histoplasmosis infection
lepromin skin test
Test
Leprosy can be an underlying cause. Anaesthetic skin patches may be seen.
Result
positive in leprosy
blastomycosis serology
Test
Associated with unilateral adenopathy on chest x-ray, enlarged spleen, and abnormal retinal exam.
Result
positive in blastomycosis infection
brucellosis serology
Test
Associated with chest x-ray findings, enlarged spleen, and abnormal retinal examination.
Result
positive in brucellosis infection
psittacosis serology
Test
Associated with bird exposure and adenopathy on chest x-ray.
Result
positive in psittacosis infection
x-ray symptomatic joints
Test
Joint symptoms and findings are associated with EN, but may also indicate rheumatological disease as underlying aetiology.
Result
abnormal in rheumatological disease
rheumatoid factor testing
Test
Joint symptoms and findings are associated with EN, but may also indicate rheumatological disease as underlying aetiology.
Result
elevated in rheumatological disease
Yersinia agglutination titre
Test
Yersinia colitis is a rare cause. May be considered if gastrointestinal symptoms are present.
Result
positive in yersinia infection
Yersinia stool cultures
Test
Yersinia colitis may be considered if gastrointestinal symptoms are present
Result
positive in yersinia infection
colonoscopy
Test
Inflammatory bowel disease is a possible aetiology, to be considered if gastrointestinal symptoms are present.
Result
abnormal in inflammatory bowel disease
serum IgD
Test
Behcet's disease may be considered if gastrointestinal symptoms are present.
Result
elevated in Behcet's disease
deep punch biopsies including subcutaneous fat, or incisional biopsies
Test
Confirmatory if clinical diagnosis is uncertain.
Does not identify the underlying cause.
Typically a septal panniculitis without vasculitis; may demonstrate Miescher's radial granuloma, which consists of a small, well-defined, nodular aggregation of small histiocytes arranged radially around a central cleft.[2]
This granuloma should not be confused with a non-caseating granuloma associated with sarcoidosis, a caseating granuloma due to tuberculosis, or a necrotising granuloma due to vasculitis.
Result
septal panniculitis: septal infiltration of neutrophils, oedema, and haemorrhage
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