TRIM21 and Hypokalemia: • Syncopal episode (previous day)• Lower limb muscle strength: 2/5 (MRC scale)• Absence of edema• Nephrotic-range proteinuria (6.544 g/24 h) (Day 1)• Albumin: 30.6 g/L (Day 1)• ANA (+, 1:1000), anti-SSA/Ro52 (+++), anti-SSB (++), p-ANCA (+), and AMA-M2 (+) (Day 1)• Hypokalemia (K+: 2.87 mmol/L)• Severe hypoalbuminemia (Alb: 20.4 g/L)