Immunodeficiencies, autoinflammatory diseases and Hansen’s disease

Abstract

Leprosy (Hansen’s disease) is an infectious disease caused by Mycobacterium leprae. However, leprosy is not an epidemic disease but an immunological disease, in which the disease phenotype is determined by the patient’s immunological status and reactions. In this review, tuberculoid and lepromatous leprosy has been located on the field of immune dysregulation, which is divided into four regions using the two axes of “immunological vector”. By locating primary immunodeficiency with sarcoid-like granulomatous lesions and Blau syndrome as a hereditary autoinflammatory disorder which the author has experienced and ordinary sarcoidosis which is important for different diagnosis of leprosy on the same field, their comparisons have been clarified. Indeed, leprosy might be a disease disappearing in the developed countries, but it has provided an indispensable model and has much contributed to the progress of immunological researches. A new problem of a reflexive infection caused by the progress of immunosuppressants has appeared and this “old and new” disorder should be still significant in the present day.