A227 CTLA-4 DEFICIENCY PRESENTING AS CROHN DISEASE IN A TEENAGE BOY WITH MULTI-SYSTEM INVOLVEMENT : A CASE REPORT

Background

Cytotoxic-T-lymphocyte-antigen-4 is a negative immune regulator. CTLA-4 deficiency can cause a complex immune dysregulation syndrome that may present as inflammatory bowel disease.

Purpose

Case Description:

A 14-year-old male presented with several years of abdominal pain, diarrhea, short stature and poor weight gain. Endocolonoscopy diagnosed Crohn disease, with patchy chronic colitis, an ileal granuloma and active duodenitis with intraepithelial lymphocytosis and villous blunting. MRE showed multiple abnormal small bowel loops. Past history included appendicitis, immune thrombocytopenic purpura and an episode each of Aeromonas, Y enterocolitica and C difficile colitis. Family history was negative for consanguinity, autoimmune conditions or immune defects.

The patient received sulfasalazine, exclusive enteral nutrition and then budesonide MMX with limited response. His pre-biologic workup identified bilateral pulmonary nodules, which were negative for infection or malignancy on further investigation. He began Adalimumab, and after 2 months had nearly normalized his fecal calprotectin to 90 ug/g. His history, together with chronic neutropenia and hypogammaglobulinemia (IgG 3.3 g/L, IgA 0.29g/L) led to a comprehensive immune and cytopenia panel, which revealed heterozygous pathogenic variants in the CTLA4 gene c.424G>C, p.(Gly142Arg), associated with CTLA-4 deficiency related immunodeficiency. Parental testing was negative, indicating a de novo mutation.

The patient was subsequently admitted to hospital with severe headache and transient aphasia. Brain MRI found hyperintense foci concerning for CTLA-4 deficiency-associated CNS inflammation. He had papilledema and lumbar puncture found increased ICP. During this admission he developed Salmonella sepsis. Repeat chest CT found extensive worsening multifocal parenchymal lesions. Extensive investigations to exclude malignancy or infection were negative, and the lung findings were felt to be Granulomatous and Lymphocytic Interstitial Lung Disease. He had elevated soluble IL-2 receptor level (2884 U/ml) and elevated CD4+PD1+ T cells in peripheral blood. Adalimumab was stopped, and he received IVIg, then Diamox with resolution of headache, followed by pulse methylprednisolone. He has since been maintained on Abatacept (a soluble CTLA-4 analog that inhibits T-cell activation). Follow up soluble IL2 receptor level was normal. PJP prophylaxis was started, as well as prophylactic dosing of IVIg and regular screening for EBV and CMV.

Method

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Result(s)

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Conclusion(s)

Discussion:

Our patient had CTLA-4 deficiency and immune dysregulation affecting multiple organs (CNS, lung, and intestinal inflammation, autoimmune neutropenia and previous ITP). Abatacept is the preferred steroid-sparing treatment of enteropathy in CTLA-4 deficiency. Soluble IL2 receptor level is an indicator of T cell activation used for treatment monitoring. This case illustrates the importance of considering immune defects even in older children presenting with apparent IBD.

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Disclosure of Interest

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INTESTINAL DISORDERS

A189 INFLAMMATORY BOWEL DISEASE IN PEDIATRIC PATIENTS POST RENAL TRANSPLANT:A CASE SERIES

Background

Diarrhea in renal transplant recipients may be due to infection, medication induced colitis and post-transplant lymphoproliferative disease. Uncommonly a subset of these children develop denovo inflammatory bowel disease (IBD), despite being already immunosuppressed. Paucity of literature in the pediatric population has been noted.

Aims

To describe the clinical presentation, investigations and response to treatment in a cohort of children diagnosed with IBD post renal transplant

Methods

Patients diagnosed with IBD post renal transplant between January 1 - October 1, 2021 at BC Children’s Hospital were identified. Medical history, symptoms at presentation, histological characteristics, results of investigations and response to treatment were reviewed

Results

Data of 3 children were collected. Ages of the children were 11, 16 and 17 years (2 female). All patients had bloody diarrhea, abdominal pain and weight loss for 1 to 2 months. IBD diagnosis was made 8, 7 and 4 years respectively post renal transplant. All children were on maintenance immunosuppression with prednisone, MMF and tacrolimus. Bacterial, viral and parasitic causes were ruled out by relevant studies. All patients had negative anti-tissue transglutaminase.

Patient 1 (transplanted for renal dysplasia) was diagnosed with Crohn disease involving the antrum, ileum, and colon with rectal sparing. Fecal calprotectin (FC) was 1742 ug/g, CRP elevated at 56mg/L. Histology showed focally active chronic gastritis and changes in ileum with cryptitis and crypt dropout. The colon had features of moderate chronic active colitis with focal severe ulceration in the rectum. The patient achieved clinical remission on treatment with methylprednisolone, then started on vedolizumab in context of rising BK virus titre.

Patient 2 (transplanted for focal segmental glomerulosclerosis) was diagnosed with indeterminate colitis involving the IC valve and scattered colonic ulcers. FC was 674 ug/g and CRP and ESR were normal. Histology showed normal ileum, moderate active chronic changes in colon and rectal sparing. Clinical remission was achieved with oral mesalamine.

Patient 3 (transplanted for Bardet-Biedl syndrome) was diagnosed with indeterminate colitis with a colonoscopy that showed patchy colonic erythema and normal ileum. FC was 966 ug/g, and CRP and ESR were normal. Histology showed patchy chronic active colitis and mild active ileitis. Clinical remission was achieved with oral and rectal mesalamine.

Conclusions

Denovo IBD occurs in children post renal transplant and must be considered in the differential for ongoing diarrhea in these patients. It can be a challenge to distinguish between IBD and other causes of diarrhea. The patients in this series entered clinical remission in a short period of time. Further exploration of the pathogenesis of IBD in these immunosuppressed patients would be valuable

Funding Agencies

None

Acute-phase protein α1-anti-trypsin: diverting injurious innate and adaptive immune responses from non-authentic threats

One would assume that the anti-inflammatory activity of α1-anti-trypsin (AAT) is the result of inhibiting neutrophil enzymes. However, AAT exhibits tolerogenic activities that are difficult to explain by serine-protease inhibition or by reduced inflammatory parameters. Targets outside the serine-protease family have been identified, supporting the notion that elastase inhibition, the only functional factory release criteria for clinical-grade AAT, is over-emphasized. Non-obvious developments in the understanding of AAT biology disqualify it from being a straightforward anti-inflammatory agent: AAT does not block dendritic cell activities, nor does it promote viral and tumour susceptibilities, stunt B lymphocyte responses or render treated patients susceptible to infections; accordingly, outcomes of elevated AAT do not overlap those attained by immunosuppression. Aside from the acute-phase response, AAT rises during the third trimester of pregnancy and also in advanced age. At the molecular level, AAT docks onto cholesterol-rich lipid-rafts and circulating lipid particles, directly binds interleukin (IL)-8, ADAM metallopeptidase domain 17 (ADAM17) and danger-associated molecular pattern (DAMP) molecules, and its activity is lost to smoke, high glucose levels and bacterial proteases, introducing a novel entity - 'relative AAT deficiency'. Unlike immunosuppression, AAT appears to help the immune system to distinguish between desired responses against authentic threats, and unwanted responses fuelled by a positive feedback loop perpetuated by, and at the expense of, inflamed injured innocent bystander cells. With a remarkable clinical safety record, AAT treatment is currently tested in clinical trials for its potential benefit in a variety of categorically distinct pathologies that share at least one common driving force: cell injury.