Targeted complement inhibition with pozelimab in children with CD55 deficiency.

CHAPLE syndrome is an ultra-rare genetic cause of protein-losing enteropathy (PLE) resulting from uncontrolled complement activation due to CD55 deficiency. We report two paediatric patients presenting with recurrent diarrhoea, hypoalbuminaemia, hypogammaglobulinaemia and growth failure, both initially evaluated as intestinal lymphangiectasia. Persistent symptoms and poor response to conventional therapy prompted genetic evaluation, which revealed pathogenic variants in the CD55 gene in both children, confirming the diagnosis of CHAPLE syndrome. Both patients required repeated albumin and intravenous immunoglobulin replacement prior to diagnosis. Targeted therapy with pozelimab was initiated. Rapid clinical and biochemical improvement was observed within 2 weeks, with sustained normalisation of albumin, total protein and immunoglobulin levels. At 3-month follow-up, both children remained in clinical remission without further need for albumin or immunoglobulin infusions. These cases highlight the importance of considering genetic causes in children with refractory PLE and demonstrate the effectiveness of early targeted complement inhibition in CHAPLE syndrome.