Investigators at University of California, San Francisco, and other centers, report a case of leptospirosis in a 14-year-old boy with severe combined immunodeficiency. He presented with headache and fever that lasted 6 days. In the previous 8 months he swam in a river in Puerto Rico and in a pool frequented by feral cats. A previous episode of fever and headache was complicated by conjunctivitis and followed by uveitis and thrombocytopenia. A recurrence of headache and fever was associated with increased CSF white cells (125/cmm) and protein (97 mg/dL), lowered glucose (24 mg/dL) and negative cultures, compatible with meningoencephalitis. He was readmitted with fever, headache, weakness, myalgias, nausea and vomiting. MRI showed T2-weighted hyperintensities in the basal ganglia and granulomatous leptomeningitis. A worsening hydrocephalus was treated with an extraventricular drain, and new-onset status epilepticus was controlled by a medically induced coma. CSF and serum samples sent for unbiased next-generation sequencing was positive for leptospira infection in the CSF but not in serum. Clinical assays for leptospirosis were negative. Treatment with high-dose intravenous penicillin G was followed by a gradual recovery over 7 days, resolution of status epilepticus, normal CSF, and resolution of leptomeningitis on serial MRI scans. PCR and serological testing at the CDC subsequently confirmed evidence of Leptospira santarosai infection. 
COMMENTARY. Leptospirosis is caused by spirochetes contracted from the urine of infected wild or domestic animals, usually while swimming in contaminated water. The incubation period is 5 to 14 days (range, 2 to 30 days). The most characteristic clinical findings are conjunctival suffusion, uveitis, and myalgias of the calf and lumbar regions . An initial septicemic phase is followed by an immune-mediated phase, complicated by purpuric rash. Duration varies from less than 1 week to several months, with occasional episodes of apparent recovery. Severity ranges from self-limited systemic illness (90% patients) to life-threatening illness with jaundice, renal failure, and hemorrhagic pneumonitis (Weil syndrome).