[BCGitis/BCGosis in children: Diagnosis, classification and exploration].

The Bacille Calmette-Guérin (BCG) vaccine is used extensively worldwide, and more than 100 million children are vaccinated each year. This is a live vaccine that protects against severe tuberculosis in children. However, BCG complications, specific to the BCG vaccine, do occur, although the epidemiology differs from one country to another. Nevertheless, these complications are considered to be rare and range from benign local BCGitis to BCGosis, a potentially lethal disseminated disease. Etiologies of BCGitis/BCGosis can be related to the vaccine itself (technical errors, vaccinal strain) or to the patient. Indeed, it is well established that some immunodeficiencies, primary or acquired, can expose the patient to BCG disease. The diagnosis of a BCG disease lies on clinical examination and laboratory results. Recent advances in molecular biology help to distinguish BCG disease from other mycobacterial infections, especially from tuberculosis. When BCG complications have been confirmed, the underlying defect should be investigated, particularly if other features of immunodeficiency are reported, such as recurrent infection, failure to thrive, etc. Prognosis largely depends on the immune status, but also on the management of the BCG disease. Although the therapeutic protocols are still controversial, there are more and more publications on the diagnosis and management guidelines of the disease.