Case Presentation: BACKGROUND: Type I hypersensitivity reactions to hemodialysis dialyzers are rare but clinically significant. They can mimic infection, autoimmune disease, or non-adherence, leading to repeated hospitalizations and delays in diagnosis.CASE: A 56-year-old Spanish-speaking woman with end-stage renal disease on hemodialysis, heart failure with reduced ejection fraction, interstitial lung disease, prior cerebrovascular accident, and type 2 diabetes mellitus was admitted multiple times within a year for missed dialysis sessions, volume overload, and suspected recurrent pneumonias. She reported recurrent nausea, chest and abdominal pain, and pruritus during dialysis, resulting in incomplete sessions.Laboratory evaluation revealed persistent absolute eosinophilia (peaking >20 K/UL) and elevated IgE (2768 IU/mL). CT chest showed multifocal opacities, while broad infectious and autoimmune work-up was unrevealing. Retrospective review demonstrated eosinophil spikes temporally associated with hemodialysis sessions. A Type I dialyzer allergic reaction was suspected. Synthetic dialyzer membrane was changed to Cellentia| Nepro (F180), after which the patient tolerated dialysis without adverse symptoms, and her eosinophil count improved.

Discussion: This case illustrates the diagnostic challenge of dialysis-related hypersensitivity. Eosinophilia in hemodialysis patients is often attributed to infection, medication, or autoimmune conditions, but dialyzer reactions remain an under-recognized etiology. Repeated hospitalizations in this patient were initially attributed to non-adherence and infection, delaying recognition of the underlying cause. Timely identification and dialyzer membrane modification prevented further intolerance and improved adherence.

Conclusions: Type I dialyzer reactions, although rare, should be considered in patients with unexplained eosinophilia and dialysis intolerance. Early recognition and appropriate dialyzer substitution can prevent recurrent hospitalizations, reduce morbidity, and optimize hemodialysis outcomes.

IMAGE 1: Absolute Eosinophils Count in relation to Cellentia Dialyzer substitution.