Systemic autoinflammatory disease, IgA glomerulonephritis and renal cortical necrosis: coincidence or causation?

We present a patient with a rare systemic autoinflammatory disease (mevalonate kinase deficiency -MKD-) with the identification of two heterozygous variants (c.1129G>A and c.32C>T) in the Mevalonate Kinase gene, detected by next generation sequencing and a highly prevalent glomerulonephritis (IgA nephropathy). The patient presents clinically with a monthly recurrent periodic fever from 12 days of age, accompanied by mucocutaneous lesions (maculopapular rash in extremities, aphthous stomatitis), joint (arthralgias in ankles, wrists and knees), lymphoid (cervical lymphadenopathy, splenomegaly), gastrointestinal (diarrhea, abdominal pain) and kidney (hematuria and proteinuria) with repeated biopsies showing IgA nephropathy alternating activity with chronicity. During follow-up. The patients presented a poor therapeutic response to multiple immunosuppressive regimens used for 7 years (corticosteroids, azathioprine, mycophenolate, cyclophosphamide, rituximab and tocilizumab), and finally a good response to canakinumab. Four years after starting canakinumab, during the course of an infection due to a muscle abscess, the clinical presentation is complicated by a severe renal microvascular event (renal cortical necrosis -RCN-) with acute kidney injury and dialysis requirement. Therecurrent episodes of inflammation due to MKD could act as triggers for the reactivation of glomerulonephritis (which would explain the poor response to immunosuppressants and the rapid progression to histological chronicity) and to generate a microenvironment that predisposes the development of RCN in the face of a non-serious infection. A defect in IgA molecules has been described in MKD, a phenomenon also observed in IgA nephropathy. This raises the challenging hypothesis of a common pathogenetic link between all the patient's clinical manifestations.