Novel CD55 Mutation Associated With Severe Small Bowel Ulceration Mimicking Inflammatory Bowel Disease in a Pair of Siblings

The complement decay-accelerating factor (DAF) is encoded by the CD55 gene.1 Lack of CD55 leads to the excess formation of the membrane attack complex (C5b-9) and overactivation of innate immunity, resulting in cell membrane disruption of various cells such as hematopoietic, endothelial, and epithelial cells.2 A case series of CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein-losing enteropathy (PLE), also known as CHAPLE disease, was first reported by Ozen et al in 2017.1 Apart from edema caused by hypoproteinemia, patients with CHAPLE disease usually present with abdominal pain, vomiting, diarrhea, and poor growth. They can develop recurrent respiratory infections due to immunoglobulin loss in the intestine. Thromboembolic conditions, autoimmune hemolysis, paroxysmal nocturnal hemoglobinuria, and atypical hemolytic uremic syndrome may also be observed among these patients. After informed consent was given, blood samples were collected from the patients and their parents. The research was performed according...