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Idiopathic CD4+ T-lymphocytopaenia with FLT1 mutation complicated by progressive multifocal leucoencephalopathy and EBV+ polymorphic lymphoproliferative disorder
  1. Noa Rippel1,
  2. Joshua Wong2,
  3. Shafinaz Hussein2 and
  4. Matko Kalac3
  1. 1Internal Medicine, The Mount Sinai Hospital, New York, New York, USA
  2. 2Pathology, Molecular and Cell Based Medicine, The Mount Sinai Hospital, New York, New York, USA
  3. 3Division of Hematology/Oncology, Department of Medicine, University of California, Irvine, California, USA
  1. Correspondence to Dr Noa Rippel; noa.rippel{at}


We describe a unique case of idiopathic CD4+T cell lymphocytopaenia complicated by viral-associated disorders in a patient with a heterozygous FLT1 mutation. A previously healthy woman presented with left-sided neurological deficits. Workup revealed a severe HIV-seronegative CD4+T cell 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 FLT1 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.

  • Infectious diseases
  • Infection (neurology)
  • Malignant and Benign haematology
  • Chemotherapy
  • Oncology

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  • Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: NR, JW, SH and MK. The following authors gave final approval of the manuscript: NR, JW, SH and MK.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests MK: Research Support – Janssen; Consultancy – Astra Zeneca, Gilead, Kyowa Kirin, Guidepoint, GLG, Seagen, Acrotech Biopharma.

  • Provenance and peer review Not commissioned; externally peer reviewed.