CD40LG and Fanconi renotubular syndrome: Although its pathophysiological mechanisms are still largely unknown, the major clinical features of IgMPC-TIN include high serum IgM (s-IgM) levels; high prevalence (> 80%) of distal renal tubular acidosis (d-RTA) [2, 3], Fanconi syndrome and positive anti-mitochondrial antibodies (AMA); and complications of primary biliary cholangitis (PBC) (46%) [2, 4] or Sjӧgren syndrome (31%) [2, 5].