Successful Early Therapy With Sirolimus for an Infant With Primary Intestinal Lymphangiectasia.

Introduction: Identifying the cause of protein-losing enteropathy (PLE) is crucial for appropriate treatment. Primary intestinal lymphangiectasia (PIL) is a cause of PLE, and low-strict fat diet with medium-chain triglyceride (MCT) supplementation may be insufficient. Sirolimus has shown efficacy in refractory PIL; however, its use in infants remains uncommon, and the optimal timing of initiation has not been established. Case Presentation: A previously healthy 7-month-old Japanese male infant presented with convulsions, generalized edema, and diarrhea. Laboratory findings revealed severe hypoproteinemia (serum albumin: 1.3 g/dL), lymphopenia (absolute lymphocyte count: 822/μL), and electrolyte abnormalities. Scintigraphy using Discussion: This case suggests one of the earliest reported responses to sirolimus in the treatment of PIL, with improvement observed within a few weeks of initiation. Early introduction of sirolimus in patients with persistent protein leakage resistant to low-strict fat diet with MCT supplementation may be associated with rapid improvement in PIL, though this hypothesis warrants further case accumulation.