Question

Normally a healthy child, Javier came to the ER with a high fever, cough and shortness of breath. After extensive testing, he was diagnosed with bacterial pneumonia and received intravenous ampicillin every 6 hrs (patient history gave no antibiotic allergy). After improvement, Javier was sent home and prescribed oral antibiotics. The next morning, Javier developed hives on his abdomen. His antibiotic was immediately stopped and he was given the anti-histamine Benadryl. Later that night, Javier developed a fever, swollen and painful ankles, & purpuric lesions caused by the hemorrhaging of blood vessels. What immunological condition explains this reaction? What would be the best tests to confirm this and what would you be looking for?

Answer 1

It is a case of Serum sickness which is type 3 hypersensitivity immune reaction.

C1q binding assay and Raji cell radioimmunoassay are confirmatory tests for this condition which detect immune complexes.

Discussion and explanation:

Serum sickness is a type 3 hypersensitivity immune reaction which is mediated by circulating immune complexes. It develops 7-14 days of initial event such as penicillin use.

Signs and symptoms:

1) Fever

2) Urticarial or maculopapular rashes

3) Lymphadenopathy (pathological and swollen lymph node)

4) Arthralgia (joint pain) and arthritis (joint inflammation)

5) Nephritis (inflammation and swelling of kidneys)

6) Vasculitis (inflammation of blood vessels) causing damage to blood vessels leading to many haemorrhagic manifestations such as petechiae, purpura or ecchymoses.

Diagnosis:

For diagnosis clinical suspicion should be high and doctor should carefully look for any sign or symptom as early as possible.

1) Complete blood count- Leukocytosis or leuucopenia, elevated eosinophil count, thrombocytopenia in some cases

2) Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein

3) Urine analysis - Proteinuria and haematuria may appear

4) Elevated immunoglobulin levels

5) Decreased complement levels

6) C1q binding assay and Raji cell radioimmunoassay for detection of immune complexes are confirmatory.

Treatment options:

Withdrawal of causative drug

Antihistaminics

Corticosteroid

Signs and symptoms usually disappear after 7-14 days due to clearing of immune complexes in the absence of offending drug.