Unusual Late-onset Enteropathy in a Patient With Lipopolysaccharide-responsive Beige-like Anchor Protein (LRBA) Deficiency.

In recent years, monogenic causes of immune dysregulation syndromes, with variable phenotypes, have been documented. Mutations in the lipopolysaccharide-responsive beige-like anchor (LRBA) protein are associated with common variable immunodeficiency, autoimmunity, chronic enteropathy, and immune dysregulation disorders. The LRBA protein prevents degradation of cytotoxic T-lymphocyte antigen 4 (CTLA4) protein, thus inhibiting immune responses. Both LRBA and CTLA4 deficiencies usually present with immune dysregulation, mostly characterized by autoimmunity and lymphoproliferation. In this report, we describe a patient with an atypical clinical onset of LRBA deficiency and the patient's response to abatacept, a fusion protein-drug that mimics the action of CTLA4.