Life Threating Hyponatremia as a Presenting Manifestation of Renal Amyloidosis

Abstract

INTRODUCTION:AL amyloidosis is a devastating, multisystem disorder that often affects the kidney and heart. Most common presentation of renal involvement is proteinuria and progressive renal failure. We present a unique case of AL-k amyloidosis presenting as life threatening hyponatremia in presence of normal kidney functions.CASE PRESENTATION:A 73 years old female presented with generalized weakness with a progression to immobility. She was becoming drowsy and difficult to be aroused. Her past medical and family history were unremarkable. She never smoked. Physical examination was unremarkable except for bilateral pedal edema. Initial biochemical labs were normal except for sodium level of 114. Both serum and urine osmolality were low. Urine sodium was low making SIADH unlikely. TSH and cortisol levels were normal. ANA, ANCA, complement level and anti GBM antibodies were negative. 24 hrs urine showed mild proteinuria. Urine protein electrophoresis was negative. Serum free light chain analysis showed increased k light chain. Skeletal survey and bone marrow biopsy were negative for myeloma. Renal biopsy confirmed AL amyloidosis. Hyponatremia initially required hypertonic saline administration. Her symptoms of altered mentation and generalized weakness resolved after sodium replacement. She was able to maintaine her serum sodium on diuretic therapy. She was further referred for chemotherapy.DISCUSSION:The kidney is one of the most frequent sites of amyloid deposition in AL. Early diagnosis is vital to start effective therapy before irreversible organ damage has occurred and should be based on markers of initial, asymptomatic organ dysfunction such as albuminuria. Glomerular renal amyloidosis presents with proteinuria while Tubulointerstitial amyloidosis presents with decreasing GFR and renal failure. Vascular involvement is accompanied by hypertension. Extraglomerular amyloidosis is rare but causes nephrogenic diabetes insipidus, which may present as hypernatremia and dehydration. Another extraglomerular manifestation is Fanconi's syndrome. None of these mechanisms explain profound hyponatremia that our patient had. In our patient likely cause is sodium depletion. Amyloidodsis may have caused inability to reabsorb sodium leading to profound sodium depletion.CONCLUSIONS:Amyloidosis in a rare disease. Diagnosis is often delayed due to insidious onset of symptoms. Renal involvement could present as profound hyponatremia requiring hypertonic saline administration. Most common presentation of renal amyloidosis is albuminuria. Therefore, unexplained hyponatremia in presence of proteinuria in an elderly patient should raise suspicion for amyloidosis. This can further be investigated with serum free light chain assay. Hyponatremia in amyloidosis responds to diuretic therapy.Reference #1:Analysis of clinical and pathological characteristics of 28 cases with renal amyloidosis. Zhu X, Liu F, Liu Y, Liu H, Xu X, Peng Y, Sun L, Yuan S.Clin Lab. 2011;57(11-12):947-52DISCLOSURE:The following authors have nothing to disclose: Ameer Rasheed, Viswanath Vasudevan, Qammar AbbasNo Product/Research Disclosure Information