A Rare Case of Type I RenalTubular Acidosis with Membranous Nephropathy Presenting as Hypokalemic Paralysis

Abstract

Type 1 renal tubular acidosis (RTA), or distal RTA (dRTA), is a disorder of renal tubular acidification, which is generally asymptomatic but may rarely present as hypokalemic paralysis. Here, we report the case of a young male who presented with sudden onset weakness of all 4 limbs and a 2-month history of swelling of the legs. An investigation revealed hypokalemia, metabolic acidosis, and nephrotic syndrome. Additional analyses revealed normal anion gap metabolic acidosis with a positive urine anion gap and dRTA. Renal biopsy showed evidence of membranous nephropathy (MN). The patient's weakness improved with potassium supplements. Normalization of the serum potassium level and disappearance of proteinuria were established with an ACE inhibitor and potassium supplementation. This case is an unusual combination of dRTA with MN coupled with the rare presenting symptoms of hypokalemic paralysis and medullary nephrocalcinosis.

Head drop and flaccid weakness in infantile nephrotic syndrome

“…[ 3 ] In the presence of hypokalemia, low urinary potassium <20 mmol/day suggests extrarenal loss or could be due to malnutrition (decreased oral intake), whereas urinary potassium >20 mmol/day suggests renal loss. [ 4 ] In the index case, urinary potassium and TTKG were low with no acidosis or alkalosis, ruling out renal losses such as renal tubular acidosis, Bartter syndrome, or primary hyperaldosteronism.…”

“…To our knowledge, only two cases of hypokalemia paralysis with nephrotic syndrome have been reported in literature till date, one had unusual combination of distal renal tubular acidosis with membranous nephropathy coupled with hypokalemic paralysis and medullary nephrocalcinosis. [ 4 10 ]…”

Acidose tubular renal distal associada à paralisia periódica hipocalêmica

“…7 A hipocalemia ocorre com frequência na ATRd. 4 Entretanto, raramente, pode se apresentar como fraqueza e paralisia muscular decorrente da perda de potássio, 7 como ocorreu com nossa paciente. Esses sintomas, que caracterizam a paralisia hipocalêmica, estão relacionados à hipocalemia severa.…”

“…3 De fato, a hipocalemia é encontrada em cerca de 28 a 53% dos pacientes com ATRd. 4 Embora a ATRd seja em geral assintomática, raros indivíduos apresentam paralisia hipocalêmica no curso de sua doença. 4 Esta é caracterizada por XPD SDUDOLVLD ÀiFLGD DJXGD DVVRFLDGD j KLSRFDOHPLD SRGHQGR acarretar complicações que ameaçam a vida, tais como arritmia cardíaca e comprometimento respiratório.…”

“…4 Embora a ATRd seja em geral assintomática, raros indivíduos apresentam paralisia hipocalêmica no curso de sua doença. 4 Esta é caracterizada por XPD SDUDOLVLD ÀiFLGD DJXGD DVVRFLDGD j KLSRFDOHPLD SRGHQGR acarretar complicações que ameaçam a vida, tais como arritmia cardíaca e comprometimento respiratório. 5 A paralisia hipocalêmica periódica corresponde a ataques recorrentes de fraqueza na presença de potássio sérico abaixo de 3,5 mEq/L.…”