Diagnosis is based on history given by patient, including recent medications. A blood sample may be taken and tested, which will show thrombocytopenia (low platelets), leukopenia (low white blood cells), high sedimentation of red blood cells, and a decrease in the complement proteins C3 and C4. A urine sample may be taken and tested, which will show proteinuria, and sometimes hematuria (blood in the urine, with hemoglobinuria). Differential diagnosis Similar skin symptoms may be caused by lupus, erythema multiforme, and hives.
Serum sickness
Erythema multiforme
Disseminated disease
Hives
Adult-onset Still's disease
Lupus
Relapsing fever
SAHA syndrome