RENAL-LOSS HYPOKALEMIA COMPLICATING FOCAL SEGMENTAL GLOMERULOSCLEROSIS PRESENTING AS NEPHROTIC SYNDROME: A RARE CASE

Introduction:

Focal segmental glomerulosclerosis (FSGS) is the most common encountered cause of nephrotic syndrome in adult patients. However, the presence of salt-wasting hypokalemia superimposing nephrotic syndrome is a rare coexistence. Hereby we report a summary of a rare case of renal loss hypokalemia suggesting Gitelman’s syndrome (GS) in FSGS.

Methods:

A 30 years-old male came to the emergency room with generalized edema. He also reported weakness over extremities and no prior history of hypertension. Hemodynamic parameters were stable, but laboratory results showed severe hypokalemia (2.3 mEq/L), metabolic alkalosis (blood pH 7.56 and HCO3- 43.8 mEq/L), profound hypoalbuminemia (1.38 g/dL), and moderate increase in urea and creatinine (61.2 and 2.27 mg/dL). There was also hyperlipidemia (Total cholesterol 285 mg/dL, LDL-cholesterol 219 mg/dL, Triglyceride 194 mg/dL) with markedly increased proteinuria (17,939 mg/day), which therefore concluded as nephrotic syndrome. He was then planned for renal biopsy. Meanwhile, electrocardiogram showed flattened U-wave consistent with severe hypokalemia which required aggressive intravenous correction. Other possible causes of hypokalemia had already been excluded, including the abnormality of thyroid hormone. Light microscopy revealed focal segmental glomerulosclerosis, mild tubular atrophy and interstitial nephritis. No significant tubular injury was observed, and immunofluorescence microscopy showed no immune deposit. The metabolic alkalosis together with renal-wasting hypokalemia (Urinary Potassium to Creatinine ratio 59.4 mmol/gram, Urinary Calcium to Creatinine ratio 0.0075 mmol/gram) suggested the patient to be classified as GS. The patient was then discharged 2 weeks after the renal biopsy performed after achieving steady state potassium level, by combining oral potassium pills and spironolactone.

Results:

The direct relationship between tubulointerstitial injury seen in glomerular proteinuria have not yet been elucidated thoroughly. Several reports demonstrate vacuolization as the most frequent finding among patients with suspicion of hypokalemic nephropathy, while our case showed only mild tubular atrophy. Several possible mechanisms contributing toward the occurrence of salt-wasting tubulopathy in nephrotic syndrome includes chronic activation of the renin-angiotensin-aldosterone pathway, which often leads to increased systemic angiotensin-II and renin level. The subsequent disturbance of hemodynamic and non-hemodynamic pathways involves the role of growth factors, which can lead to both apoptosis and non-apoptotic detachment of podocyte foot processes. Another hypothesized mechanism responsible for the tubulointerstitial injury suggesting GS is the salt-wasting induced by interstitial nephritis, as demonstrated in this case, which thought to be the extension of surrounding glomerular injury. However, a serial biopsy is needed to explain a complete pathological process.

Conclusions:

Salt-wasting tubulopathy co-existing with nephrotic syndrome is a rare occurrence. The exact initial triggering mechanism might not be recognized, but the interaction between the two entities may complicate management and prolong the recovery process.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.