{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,28]],"date-time":"2025-08-28T00:05:57Z","timestamp":1756339557288,"version":"3.44.0"},"reference-count":30,"publisher":"BMJ","issue":"8","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2023,7,23]]},"published-print":{"date-parts":[[2023,8]]},"abstract":"<jats:p>We describe a unique case of idiopathic CD4+T\u2009cell lymphocytopaenia complicated by viral-associated disorders in a patient with a heterozygous <jats:italic>FLT1<\/jats:italic> mutation. A previously healthy woman presented with left-sided neurological deficits. Workup revealed a severe HIV-seronegative CD4+T\u2009cell deficiency and white matter brain lesions; brain biopsy confirmed progressive multifocal leucoencephalopathy (PML). Six years later, she represented with a tender mandibular lesion, with pathology diagnostic for EBV+polymorphic post-transplant-like lymphoproliferative disorder. A heterozygous <jats:italic>FLT1<\/jats:italic> P1127L mutation was detected on peripheral blood and mandibular lesion next-generation sequencing. Concern for PML reactivation with rituximab-based therapy and the presence of localised disease led us to offer radiotherapy, resulting in significant symptom relief and marked therapeutic response on repeat imaging.<\/jats:p>","DOI":"10.1136\/bcr-2022-253105","type":"journal-article","created":{"date-parts":[[2023,8,29]],"date-time":"2023-08-29T12:55:44Z","timestamp":1693313744000},"page":"e253105","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Idiopathic CD4+ T-lymphocytopaenia with <i>FLT1<\/i> mutation complicated by progressive multifocal leucoencephalopathy and EBV+ polymorphic lymphoproliferative disorder"],"prefix":"10.1136","volume":"16","author":[{"given":"Noa","family":"Rippel","sequence":"first","affiliation":[{"name":"Internal Medicine, The Mount Sinai Hospital, New York, New York, 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