Differentials
Bacterial adenitis
SIGNS / SYMPTOMS
Painful swollen lymph nodes with local evidence of skin involvement.
INVESTIGATIONS
Gram stain and culture of bacteria from lesion
Gram stain: positive
Culture: Staphylococcus aureus or group A Streptococcus (S pyogenes).
Infectious mononucleosis
SIGNS / SYMPTOMS
Fever, cervical lymphadenopathy, pharyngitis, rash, periorbital oedema, hepatosplenomegaly.
INVESTIGATIONS
FBC: lymphocytosis, atypical lymphocytosis.
Heterophile antibodies: positive.
Epstein-Barr virus (EBV) serology: positive for EBV-specific antibodies (viral capsid antigen [VCA]-IgM, VCA-IgG, early antigen, Epstein-Barr nuclear antigen).
Real-time polymerase chain reaction: EBV DNA detection.
Cytomegalovirus infection
SIGNS / SYMPTOMS
Fever, lymphadenopathy, hepatomegaly.
INVESTIGATIONS
Cytomegalovirus polymerase chain reaction or serum antigen test: positive.
Toxoplasmosis
SIGNS / SYMPTOMS
Painless, firm lymphadenopathy, generally confined to one chain of nodes, most commonly cervical.
Other manifestations include low-grade fever, hepatosplenomegaly, and rash.
INVESTIGATIONS
Toxoplasma serology (IgM, IgG antibodies): positive.
Polymerase chain reaction: positive.
Kaposi's sarcoma
SIGNS / SYMPTOMS
Bacillary angiomatosis may look like Kaposi's sarcoma. Difficult to differentiate clinically.[51]
Oral lesions may be present.
INVESTIGATIONS
Skin/mucosal biopsy with histopathology: characteristic vascular lesion with atypical spindle-shaped cells.
HIV infection
SIGNS / SYMPTOMS
Generalised lymphadenopathy and low-grade fever may occur as a result of uncontrolled viraemia.
INVESTIGATIONS
HIV serology by enzyme-linked immunosorbent assay (ELISA): positive.
Western Blot assay: positive.
Serum HIV rapid test: positive.
Hodgkin's disease
SIGNS / SYMPTOMS
Typically bimodal presentation, peaking in young adults (15-35 years) and adults >55 years.
Most cases (80%) have involvement of cervical and above the diaphragm lymph nodes.
Some present with 'B symptoms' such as weight loss, night sweats, and fever.
INVESTIGATIONS
Biopsy of lymph node confirms pathological features.
Tuberculosis lymphadenopathy
SIGNS / SYMPTOMS
Associated with prolonged duration of fever, night sweats, weight loss; usually accompanied by lung findings.
INVESTIGATIONS
Lymph node aspirate and sputum culture: positive for acid-fast bacilli.
Chest x-ray: middle and lower lung zone infiltrates.
Tuberculin skin test: positive (millimetres of induration).
Interferon-gamma release assays: positive.
Atypical mycobacterial lymphadenopathy
SIGNS / SYMPTOMS
Isolated or multiple cervical lymphadenopathy, associated with prolonged duration of fever, night sweats, weight loss.
INVESTIGATIONS
Excision biopsy and culture: positive for acid-fast bacilli.
Adenoviral syndrome
SIGNS / SYMPTOMS
Fever with conjunctivitis and lymphadenopathy, in any age group.
INVESTIGATIONS
Adenoviral serology: a 4-fold rise in acute titres to convalescent titres is diagnostic.
Polymerase chain reaction: positive.
Tularaemia
SIGNS / SYMPTOMS
Typically presents with abrupt onset of fever, with chills and rigors .
History of travel to endemic area or recent hunting with exposure to rabbits, hares, and muskrats.
INVESTIGATIONS
Culture of blood or other tissue samples: positive growth.
Microscopy: organisms identified with bipolar staining on Giemsa's stain.
Direct fluorescent antibody test for Francisella tularensis: positive.
Serology: 4-fold rise or a single titre of >1:128 by micro-agglutination assay.[52]
Salmonella infection
SIGNS / SYMPTOMS
Prolonged febrile illness usually accompanied by high-grade fever, chills, rash, and gastrointestinal symptoms.
INVESTIGATIONS
Blood culture: positive
Blastomycosis
SIGNS / SYMPTOMS
History of travel to endemic area; fever and lymphadenopathy with skin lesions and/or respiratory symptoms.
INVESTIGATIONS
Chest x-ray: lung infiltrates with hilar adenopathy
Sputum smear and culture: large, oval, broad-based budding yeast
Serology: positive
Brucellosis
SIGNS / SYMPTOMS
Fever, history of exposure to cattle, lymphadenopathy.
INVESTIGATIONS
Biopsy: positive for Brucella organisms.
Serology test (serum agglutination test): detects antibodies against B abortus, B suis, B melitensis, and B canis.
Polymerase chain reaction: positive.
Lyme disease
SIGNS / SYMPTOMS
History of tick exposure, erythema migrans skin lesion.
INVESTIGATIONS
Lyme-specific IgM and IgG: positive.
Skin biopsy culture: positive culture is likely from biopsy specimens from erythema migrans lesions, but is less likely in serum and cerebrospinal fluid samples.
Polymerase chain reaction: positive results in later stages of infection.
Malaria
SIGNS / SYMPTOMS
B bacilliformis can cause a febrile illness similar to malaria with severe anemia, and both are associated with mosquito bites.
INVESTIGATIONS
Giemsa-stained thick and thin blood smears: detection of asexual or sexual forms of Plasmodium species inside erythrocytes.
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