IGHA1 and hereditary spastic paraplegia: The similarities between primary IgAN and HSP-IgAN have been stressed since a long time, but recently the common pathogenesis was demonstrated [25,26] with data on the autoantigen, galactose-deficient IgA1, and specific autoantibodies (IgG and IgA subclasses); a common genetic background for this galactose-deficient IgA1 was also described [27].