Glomerulopathy in patients with dermatomyositis in early active disease: clinical, pathological and capillaroscopic manifestations, and response to treatment.

Introduction: Idiopathic inflammatory myopathies (IIMs) are a group of systemic connective tissue diseases that present with muscular and extra-muscular manifestations. There are few reports on kidney involvement, especially in dermatomyositis (DM) patients. We evaluated the clinical, laboratory, capillaroscopy, and kidney pathology of patients with DM, who presented with proteinuria during the first year, and followed them for response to treatment.

Material and methods: We evaluated 205 patients with proximal muscle weakness or high muscle enzymes, who referred to the nailfold capillaroscopy clinic from April 2010 to October 2021. Seventy-four patients fulfilled the New 2017 EULAR/ACR Classification Criteria for adult and juvenile IM with probability of ≥ 90% for DM with duration of ≤ 12 months and proteinuria > 350 mg/24 hours. All manifestations of patients with glomerulopathy and their kidney biopsies were reviewed, and they were followed for their treatment response.

Results: From 74 patients with DM, 52 female and 22 male, median age 37 (19-65) years, and disease duration of median 4.5 (1-12) months, 2 (2.7%) patients (25- and 28-year-old male) had proteinuria. Their kidney biopsy showed mesangioproliferative glomerulonephritis (GN). There was no case of acute or chronic kidney damage or rhabdomyolysis. Both had high disease activity, high erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), abnormal capillaroscopy, and high anti-Ro positivity with good early response of their kidney function, muscle weakness, and laboratory tests after immunosuppressive treatment for 3-6 months. One patient had capillaroscopy follow-up, and all abnormalities were resolved in 8 fingers. One patient, due to poor follow-up, after 8 months had recurrence of his disease.

Conclusions: We found mesangioproliferative GN as a rare extra-muscular manifestation in patients with DM in the active and early phase of the disease. Full immunosuppressive treatment showed early complete recovery in these patients.