Abstract / Summary
Abstract Background : Dermatomyositis is an idiopathic inflammatory myopathy that can involve multiple organ systems. However, its coexistence with bullous pemphigoid and membranous nephropathy is extremely rare, and no cases with concurrent diabetes mellitus have been reported to date. We present a rare case of dermatomyositis complicated by bullous pemphigoid, stage II membranous nephropathy, and diabetic ketosis, and discuss the clinical features, diagnostic and therapeutic course, and outcomes of combined immunosuppressive therapy. Case presentation : A 55-year-old male patient presented with generalized erythema, papules, and pruritus for over 2 months, having visited multiple hospitals without a definitive diagnosis. Upon admission, marked hyperglycemia and positive urinary ketones were noted; the endocrinology department diagnosed diabetic ketosis. Further investigations revealed positive anti-Jo-1 antibodies, massive proteinuria (24-hour urinary protein 7.5 g), hypoalbuminemia (20.1 g/L), and renal dysfunction (serum creatinine 106 μmol/L). After transfer to our department, myositis antibody profiling demonstrated dual positivity for anti-Jo-1 and anti-PM-SCL100 antibodies. Skin biopsy with direct immunofluorescence showed linear IgG and C3 deposition along the basement membrane zone, and renal biopsy confirmed stage II membranous nephropathy. Serum anti-PLA2R antibody and renal tissue PLA2R/THSD7A staining were both negative, supporting a secondary etiology of membranous nephropathy. The patient was diagnosed with dermatomyositis, bullous pemphigoid, stage II membranous nephropathy, and diabetes mellitus. He was treated with methylprednisolone combined with mycophenolate mofetil, tacrolimus, and hydroxychloroquine, along with intensive glycemic control. At 10-week follow-up, 24-hour urinary protein decreased to 0.26 g, serum albumin increased to 36.3 g/L, serum creatinine was 98 μmol/L, skin lesions completely resolved with no residual pruritus, and glycemic control was stabilized (HbA1c decreased from 9.5% to 6.2%). No severe adverse events occurred. Conclusions: This case represents a previously unreported coexistence of dermatomyositis with bullous pemphigoid, stage II membranous nephropathy, and diabetic ketosis. The combination regimen of glucocorticoids, mycophenolate mofetil, tacrolimus, and hydroxychloroquine demonstrated favorable efficacy and safety for this complex overlap syndrome. This case suggests that in dermatomyositis patients presenting with bullous skin lesions or massive proteinuria, active screening for overlapping autoimmune skin disorders and glomerular diseases is warranted, and early combined immunosuppressive therapy may improve outcomes.