Incidence and consequences of varicella in children treated for cancer in Guatemala.

BACKGROUND: Varicella-zoster virus infection is associated with significant morbidity and mortality in immune-compromised children, despite treatment with antiviral agents. Universal varicella vaccine programs have significantly decreased this risk in many highincome countries, but in most low-income and middleincome countries, the burden of varicella in children treated for malignancy is poorly defined. METHODS: We retrospectively reviewed records of children at the National Unit of Pediatric Oncology (UNOP) in Guatemala diagnosed with varicella between January 2009 and March 2013 in order to calculate incidence of varicella and evaluate morbidity, mortality, treatment interruption, and cost. RESULTS: Fifty-nine cases of varicella were identified. Incidence was 23.4 cases per 1000 person-years (p-y). 66.1% of cases occurred in children with leukemia (median age 5.2 years; interquantile range 3.4-7 years) and 41.0% of these occurred during maintenance therapy. Source of exposure was identified for 14/59 (23.7%) children. Most were hospitalized (71.2%) and given intravenous acyclovir (64.4%). Eight (13.6%) children required critical care, and two (3.4%) died from disseminated varicella with multiorgan failure. Chemotherapy was delayed or omitted due to varicella in 50%. No significant differences in outcomes based on nutritional and immunologic status were detected. The minimum average cost of treatment per episode was 598.75 USD. CONCLUSIONS: Varicella is a significant problem in children treated for cancer in Guatemala, where effective post-exposure prophylaxis is limited. In the absence of universal varicella vaccination, strategies to improve recognition of exposure and the future use of novel inactivated vaccines currently under investigation in clinical trials could mitigate this burden.

"Ghosts in my body": Seizure-like presentation of hypocalcemic tetany secondary to hypomagnesemia in a patient receiving cetuximab therapy for metastatic medulloblastoma.

Cetuximab, a monoclonal antibody specific for epidermal growth factor receptor, is increasingly used off-label and in early-phase trials for pediatric malignancies. Here, we report a patient with metastatic medulloblastoma receiving therapy with cyclophosphamide, vinblastine, and cetuximab. During evaluation for possible seizures, he was noted to be severely hypocalcemic, hypokalemic, and hypomagnesemic, a consequence of the blockade of renal epidermal growth factor receptor expression. His symptoms rapidly abated with intravenous electrolyte repletion. This case highlights the clinical heterogeneity of tetany and the importance of careful laboratory screening for known adverse effects of chemotherapy, particularly when newer biological agents are used off-study in combination chemotherapeutic regimens.