Disseminated Varicella-Zoster Virus in a Patient on Pegloticase and Mycophenolate Mofetil for Gout

There are various treatments for managing gout, including combination treatment with immunomodulators. However, these treatments can lead to significant immunosuppression, potentially leading to worse health outcomes, such as the one described in this case. We present the case of a 70-year-old female patient with a past medical history of atrial fibrillation, type 2 diabetes mellitus, and gout, who presented with progressively worsening altered mental status. This ultimately necessitated intubation, as well as the initiation of vasopressor support for new, worsening hypotension. She was noted to have a widespread vesicular pruritic rash present for the past month. Swabs of the vesicular lesions resulted positive for varicella-zoster virus (VZV). Her serum was also VZV positive, with 6,800,000 copies/mL detected. She later developed bilateral patchy infiltrates, and a bronchoscopy showed patchy erythema in multiple proximal airways. A lumbar puncture was performed due to the patient's altered mental status, which showed VZV (<200 copies) in her cerebrospinal fluid (CSF). She was, therefore, started on acyclovir, and she clinically improved. Her final diagnosis was disseminated VZV with multiorgan involvement, including the lung, skin, liver, and CSF. Medication review revealed that the patient was taking mycophenolate mofetil (MMF) and pegloticase for the treatment of gout. It was thus suspected that the MMF led to an immunocompromised state, which predisposed her to disseminated VZV.  Pegloticase is a Food and Drug Administration (FDA)-approved treatment for refractory gout but is known to be highly immunogenic. To reduce pegloticase's immunogenicity, MMF is often co-administered. In this case, our patient became profoundly immunosuppressed with the MMF-pegloticase regimen, which led to disseminated VZV. This case sheds light on the serious risks associated with this drug regimen.