MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II DEFICIENCY NEEDS AN EARLY DIAGNOSIS - REPORT OF A CASE

Major histocompatibility complex (MHC) class II deficiency is a rare p rimary immunodeficiency disorder characterized by defects in human leu kocyte antigen class II expression, inconsistent expression of human l eukocyte class I molecules, and a lack of cellular and humoral immune responses to foreign antigens. Clinical onset occurs early in life wit h recurrent infections and chronic diarrhea. The prognosis is poor, an d mean age at the time of death is 4 years. The only curative treatmen t is bone marrow transplantation (BMT), which allows the immune system 's reconstitution. BMT should be done early in life, because long-term survival seems to depend on the number of previous viral infections. We report the case of an MHC class II deficiency discovered late in a 4-year-old girl by means of immunohistochemistry of small bowel biopsy revealing the absence of MHC class II expression. The child received a BMT twice but died because of a overwhelming viral infection. This c ase underlines the necessity to explore children presenting with infec tions and chronic diarrhea in order to find MHC class II deficiency. U sually, diagnosis is performed on cytospins, but when it has been miss ed clinically, it can be performed by using immunohistochemistry on sm all bowel biopsies.