[A case of bronchiolitis due to pneumocystis lung infection related to major histocompatibility class II deficiency].

UNLABELLED: Despite occurring commonly in children bronchiolitis can also be the presenting feature of other disorders particularly congenital malformations and immunological diseases. We report a rare and severe cause of bronchiolitis: major histocompatibility (MHC) class II deficiency, an autosomal recessive disease.

CASE REPORT: An eight month old infant was admitted with hypoxic bronchiolitis. An immunodeficiency disease was suspected based on lingering symptoms associated with poor weight gain. Microbiologic tests revealed an infection with Pneumocystis carinii and immunologic investigations allowed us to make the diagnosis of MHC class II deficiency.

DISCUSSION: The lack of MHC class II expression results in a severe defect in both humoral and cellular immune responses to foreign antigens. It is characterised by recurrent bronchopulmonary infections and chronic diarrhoea. The clinical onset occurs within the first months of life. Prognosis is very poor when bone marrow transplantation cannot be performed.