A Rare Case of Type I RenalTubular Acidosis with Membranous Nephropathy Presenting as Hypokalemic Paralysis
A 20-year-old male presented with a 2-month history of on and off swelling of both legs and sudden onset weakness of all 4 limbs without any history of loss of consciousness, seizure, headache, sensory loss, or bowel and bladder involvement. There was no history of such a weakness. Additionally, there was no history of dryness of the mouth and eyes (suggestive of Sjögren's syndrome), no joint pain, oral ulcers, hair loss, or photosensitivity (suggestive of lupus). A neurological examination revealed normal cranial nerves and higher mental functions. Power in the upper and lower limbs was 2/5 and 1/5, respectively. His deep tendon reflexes were diminished, with no plantar response; however, sensory function remained intact.\nThe patient's laboratory profile was as follows: hemoglobin: 10.8 g/dl, total leukocyte count: 14,300/mm3, platelet count: 2.8 × 105/mm3, urinary protein: 3+, urinary sugar: 0, urine microscopy: white blood cell count: 4-6/high-power field, red blood cell count: 2-4/high-power field, urinary pH: −6.5, 24-hour urinary protein: 3.3 g/day, serum albumin: 2.1 g/dl, serum cholesterol: 526 mg/dl, serum triglycerides: 346 mg/dl, C3: 79.6 mg/dl (normal range: 80-160), C4: 62.8 mg/dl (normal range: 20-40), HBsAg: negative, anti-HCV: negative, HIV I and II: negative, anti-Ro and anti-La antibodies: negative, blood urea: 29 mg/dl, serum creatinine: 1.2 mg/dl, random blood sugar: 88 mg/dl, corrected serum calcium: 9.4 mg/dl, serum sodium: 143 mEq/l, serum potassium: 2.0 mEq/l, serum chloride: 120 mEq/l, serum PO4: 4.3 mEq/l, arterial blood gas: pH 7.2, pCO2: 31 mm Hg, pO2: 104 mm Hg, HCO3: 12.5 mEq/l, anion gap: 10.5 mEq/l (normal range: 10-12).\nThe urine anion gap (UAG) [Na+ + K+ – Cl- (70 + 25 − 65 = 30)] was positive. Urinary pH was <5.5 and the fractional excretion of bicarbonate (FeHCO3) was found to be 2, after intravenous infusion of sodium bicarbonate. Thus, the diagnosis of dRTA was established. Ultrasonography showed normal-sized kidneys with nephrocalcinosis of the medulla (suggestive of type 1 RTA), mild right-sided pleural effusion, and moderate ascites. A renal biopsy showed a thickened basement membrane with subepithelial spikes (fig. , fig. ). The interstitium showed mild mononuclear cell infiltrate and fibrosis with tubular involvement (fig. ). Immunofluorescence was positive for IgG and C3 (fig. ). Thus, the diagnosis of MN was made.