CHAPLE syndrome (complement hyperactivation, angiopathic thrombosis, protein losing enteropathy) is a newly discovered genetic disorder, which is caused by deleterious mutations in the CD55 gene. Patients often suffer from chronic manifestations that may lead to life-threatening complications despite conventional treatment options.The cause of gastrointestinal protein loss is distorted lacteals in the gut, referred to as primary intestinal lymphangiectasia (PIL). There is a second group of patients with PIL with intact CD55, referred to here as "non-CHAPLE PIL". The current study aims to explore the signatures of CHAPLE and non-CHAPLE PILs, discover druggable molecular targets and identify biomarkers that can direct therapy. A subgroup of patients with CHAPLE syndrome receive treatment with a complement C5 blocker, eculizumab, on an off-label basis. This study involves serial transcriptome and metabolic profiling of biological samples under eculizumab therapy and correlates them with the clinical response. Overall, the aim of this research is to integrate clinical data and high-throughput metabolic profiling approaches to better characterize the etiology of PILs and develop novel therapeutic approaches.

CHAPLE syndrome is a newly discovered genetic disorder characterized by excessive loss of proteins in the gastrointestinal tract, referred to as protein-losing enteropathy. The disease typically presents in early childhood with facial and extremity edema in relation to hypoalbuminemia, chronic diarrhea, failure to thrive and, in extreme cases, severe thromboembolic disease that can lead to premature death. Patients afflicted with this newly discovered disease have been treated with conventional medications, including inflammatory bowel disease drugs to reduce gastrointestinal inflammation, albumin and immunoglobulin replacement therapy, dietary modification, supportive measures to supplement micronutrients and vitamins, surgery to remove affected intestinal segments, among others. These interventions have often provided only partial relief, with no capacity to alter the natural course of the disease.

CHAPLE syndrome is caused by loss of a complement regulatory protein due to deleterious mutations in the CD55 gene, which results in excessive activation of the complement system. Based on the scientific observations that complement hyperactivation is the primary event that underlies disease manifestations, it was hypothesized that complement inhibition therapy can potentially reverse the pathological processes. Through a compessionate program 3 CHAPLE patients from a single family have been treated with a complement C5 blocker antibody called eculizumab, with favorable response (Kurolap et al. PMID: 28657861). While these observations confirm the primary role of complement hyper activation in PIL associated with CHAPLE syndrome, the pathogenesis of PILs not related to CD55 deficiency (non-CHAPLE PIL) remains unknown. It is hypothesized that that there may be pathogenetic intersections between CHAPLE and non-CHAPLE PILs.

Following a clinical observation that eculizumab provides a rapid clinical relief in unrelated CHAPLE patients based in Turkey similar to Kurolap et al.'s report, researchers of this study decided to evaluate the clinical outcome of eculizumab among subsequent CHAPLE patients who are placed on this therapy. In parallel, molecular investigations on biological samples under eculizumab therapy are being carried to dissect the key alterations under complement C5 blockade.

The current study is based on use of high-throughput methods to investigate PILs, including exome sequencing (for the non-CHAPLE PILs), transcriptomics, proteome and microbiome investigations. The aims of the study include; 1. Discovery of signatures and biomarkers in CHAPLE, 2. Identification of the molecular etiology of non-CHAPLE PILs and potentially discover novel gene defects. The integrated application of genomics, transcriptome, proteomics and microbiome aims to identify key mediators and pathways operative in the pathogenesis of intestinal lymphangiectasias. Serial evaluation and longitudinal follow up of patient samples under eculizumab (anti-complement C5 antibody) therapy investigates dynamic alterations in the pathological profiles in CHAPLE syndrome. It is anticipiated that these studies will improve the diagnosis and treatment of CHAPLE and related conditions.

Goals of the current study include:

1. To discover novel gene defects underlying PILs not related to CD55 deficiency.

2. To identify signatures of CHAPLE disease and non-CHAPLE PILs that may reveal key mediators of disease and additional novel therapeutic targets.

3. To explore the efficacy of eculizumab in a larger group of CHAPLE patients from unrelated families, with variable degree of disease severity.

4. To analyze patient samples collected before and during eculizumab therapy with the following objectives:

   1. To understand relations between eculizumab concentration, complement function (CH50, AH50) and complement protein levels (C3, C5, CFB, C3a, C5a, sC5b-9, Bb, Ba)
   2. To explore biomarkers of inflammation and thrombosis, complications of the disease that can occur in certain affected individuals.

Inclusion Criteria:

1. Patients diagnosed with PIL form the study groups and deem eligible for the study unless there is a risk associated with blood draw.
2. The patients with CHAPLE syndrome who receive eculizumab therapy and consent to participate in this study are followed prospectively and clinical data collected. Biological sample collection and molecular investigations are to be made only if the patient is willing to provide biological samples, including peripheral blood and stool.

Exclusion Criteria:

1. Presence of a concomitant disease that leads to hypoproteinemia at the time of starting eculizumab such as a urinary protein loss or a hepatic disease that affects production of proteins by liver.
2. A concomitant disease that leads to secondary intestinal lymphangiectasia such as a fontan procedure for congenital heart disease.
3. Unstable clinical condition not allowing blood draw, such as severe anemia.

All PIL patients, including CHAPLE and non-CHAPLE PILs are to be included in the study.Among the CHAPLE patients who receive eculizumab therapy a prospective follow-up is made. Age matched healthy subjects form the control group.