title: Selective immunoglobulin A deficiency associated with modular lymphoid hyperplasia.
abstract: Nodular lymphoid hyperplasia (NLH) has been firmly associated with syndromes of hypogammaglobulinemia but not with selective absence of IgA. We report the case of a 5-yr-old girl with the triad of selective IgA deficiency, NLH of the small bowel, and giardiasis. Results of an extensive immunologic investigation, including immunohistochemical examinations of small bowel biopsies, support the hypothesis that the basic defect responsible for IgA deficiency in this patient was the failure of precursor IgM-bearing lymphocytes to differentiate into IgA-producing plasma cells. Furthermore, the abundance of IgM-bearing cells in biopsy specimens demonstrates the existence of a compensatory mechanism in the intestine to substitute IgM for the absent IgA.
mesh_terms: D002675:Child, Preschool; D004406:Dysgammaglobulinemia / Q000150:complications* / Q000276:immunology; D005260:Female; D005873:Giardiasis / Q000150:complications; D006801:Humans; D006965:Hyperplasia / Q000150:complications / Q000276:immunology; D007109:Immunity; D007111:Immunity, Cellular; D007070:Immunoglobulin A; D007075:Immunoglobulin M; D007421:Intestine, Small / Q000473:pathology*; D008221:Lymphoid Tissue / Q000473:pathology*
chemical_list: D007070:Immunoglobulin A; D007075:Immunoglobulin M