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Kidney Week

Abstract: TH-PO704

Unveiling a Novel Link: A Case of Secondary FSGS with Anti-MDA5 Amyopathic Dermatomyositis

Session Information

Category: Glomerular Diseases

  • 1402 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Vaddadi, Sneha Madhuri, UC Davis Health, Sacramento, California, United States
  • Ananthakrishnan, Shubha, UC Davis Health, Sacramento, California, United States
  • Madan, Niti, UC Davis Health, Sacramento, California, United States
  • Jen, Kuang-Yu, UC Davis Health, Sacramento, California, United States
  • Wiegley, Nasim, UC Davis Health, Sacramento, California, United States
Introduction

Amyopathic dermatomyositis is a cutaneous predominant form of dermatomyositis, characterized by the biomarker anti-MDA5 antibody. Extra-dermatologic involvement has been shown within the pulmonary, vascular, or articular systems. No known reports demonstrate an association between this rarer form of dermatomyositis and glomerular disease. We report a case of anti-MDA5 dermatomyositis associated focal and segmental glomerulosclerosis (FSGS), treated with immunosuppressive therapy targeting the underlying autoimmune condition.

Case Description

A 56-year-old Black man with confirmed anti-MDA5 positive amyopathic dermatomyositis diagnosed via skin biopsy and otherwise negative myositis panel presented for nephrotic syndrome and acute kidney injury evaluation. Labs showed serum creatinine of 2.04 mg/dL (baseline 0.8), urine protein to creatinine ratio >7 g/g, serum albumin of 2.6 g/dL, and urinalysis without cellular sediment. A native kidney biopsy was performed, showing features of FSGS on light microscopy (LM), negative immunofluorescence (IF), with segmental foot process effacement and the presence of tubuloreticular inclusions on electron microscopy (EM). Malignancy workup was negative. The patient was treated with high-dose prednisone and mycophenolate mofetil (MMF) for targeted treatment of both dermatomyositis and FSGS, with subsequent improvement to partial remission in the first 6 months.

Discussion

To our knowledge, this is the first reported case of kidney involvement with amyopathic dermatomyositis. With an otherwise negative workup for other viral or malignant causes, the likely etiology of secondary FSGS was this autoimmune condition. MMF, a common treatment for dermatomyositis, was utilized in this case for targeted treatment of both dermatomyositis and FSGS and resulted in improved proteinuria and partial remission of nephrotic syndrome.

Figure 1: A. Periodic Acid Schiff stain showing segmental glomerulosclerosis.
B. Tubuloreticular inclusion on Electron Microscopy