Conclusion
Joint involvement and recurrent infections with hypogammaglobulinemia are variable in LRBA deficiency, hence it should always be kept in mind as a differential diagnosis for a patient with these conditions. In this case, arthritis was the first presenting condition followed by pneumonia, and according to the episodes of recurrent infection, hypogammaglobulinemia, and poor response to immunizations, CVID was suggested as the possible diagnosis. Fecal calprotectin level was increased during bacterial infection and as disease severity increased. This being considered, fecal calprotectin level may be a useful marker for application in children with LRBA deficiency during infectious diarrhea. In this patient, we found two novel mutations in two different gene loci (TCF3 and LRBA ) which were both classified asVariant of Uncertain Significance (VUS) . Validation of these detected variants by another molecular method such as PCR-Sanger sequencing is recommended. Also, more effort should be made to resolve VUS classification as pathogenic or benign. This can be achieved by investigating and functional analysis of these variants in a sufficient number of families. Based on this analysis, a more accurate classification of variants could be reached.