Hypokalemicparaperesis unmasks Sj?gren’s disease GhoshS, Mondal S, Chandra S K, Bandyopadhyay S Keywords:Hypokalemia, Paraperesis, Distal Renal tubular acidosis, Sj?gren’s Syndrome A 51 year oldfemale presented to the emergency department with complaint of both lower limbprogressive and painless weakness and inability to stand and walk for last 24hours. She also mentioned that she had three episodes of vomiting but no loosemotion and fever. She was on treatment with beta-blockers and sulfonylurea forhypertension and type-II diabetes mellitus. Review of her medical history wasnot contributory to find any medications or previous or familial illnessleading to this flaccid paraperesis.

Neurological examination revealed grade 1and grade 2 power (MRC grading) in left and right lower extremitiesrespectively along with depressed deep tendon reflexes but no sensory signs andautonomic dysfunction. Other physical examination findings includingophthalmological examination were unremarkable.  At the timeof admission, her blood pressure was 150/80mmHg. Initial arterial blood gasrevealed hyperchloremic metabolic acidosis with normal anion gap and severehypokalemia. Routine electrocardiogram had presence of large ‘U’ waves.

Bloodchemistry showed random sugar 180mg/dl, sodium 132 mmol/l, potassium 1.7mmol/l, chloride 112mmol/l, bicarbonate 11mmol/l, creatinine 0.9 mg/dl, calcium9.7 mg/dl, phosphorus 1.

3 mg/dl and magnesium 1.4 mg/dl. Spot urinary potassiumwas measured and found to be 24 mEq/l. Urine routine examination revealedurinary pH of 7.0 but no cast and red blood cells. Electrolyte replacement wasstarted following which her clinical condition improved and there was noresidual weakness.

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Specific laboratory parameters including serum thyroidstimulating hormone (1.5 uIU/ml), creatine kinase (248 U/L), vitamin B12 (564pg/ml) and liver function test were found to be within normal limit.  A diagnosis of distal renal tubular acidosis(dRTA) type-I was considered on the basis of hyperchloremic metabolic acidosis,alkaline urinary pH, spot urinary potassium of 24 mEq/l and low plasmabicarbonate. Ultrasound examination showed normal kidneys with nonephrocalcinosis or stones. Autoimmune work up was sent inorder to find the cause of dRTA as autoimmune disorders including sjogrens’syndrome, rheumatoid arthritis, systemic lupus erythematosus and autoimmunehepatitis remained major secondary etiologies in the absence of other causativemedications. Though our patient denied to have any history of joint pain, rashand classical sicca symptoms. Her antinuclear antibody (ANA) level was found tobe 4 positive in 1:100 dilution (fine granular pattern), RA factor and anti-CCPwere 27 IU/ml and 1.

1 U/ml. Complete ANA profile by line blot assay showed 3positive antibody titer to SS-A, SS-B and Ro-52.  Serum protein electrophoresis was normal.  A lip biopsy could not be done as they patientdidn’t give consent in the view of absence of any classical dry symptoms. Diagnosisof primary SS was considered on the basis of nephrological involvementpresented as dRTA and positive auto-antibody results. She wastreated with oral prednisolone on tapering dose starting with 40mg/day andgradual tapering to a stable dose of 10mg/day. After one month of follow up herserum bicarbonate was 24 mEq/l and potassium was 3.

9 mEq/l.  Discussion:Sj?gren’ssyndrome (SS), known to occur more in the 40–45 years age groupwith a female predominance of 10:1, is a chronic autoimmuneinflammatory disease featuring both exocrine gland malfunction and extra-glandularinvolvement. Most of the times, a diagnosis of  SS is only thought when symptoms like dry eye,dry mouth are present in clinical practice. But there are handful of cases inliterature which show that even in the absence of classical sicca symptoms, adiagnosis of SS is made. Extra-glandular involvement of SS includes skin,joints, lung, heart, gastro-intestinal tract, thyroid, kidney, bladder and bothcentral and peripheral nervous system. Prevalence of renal involvement in SSwas found to be 2 to 67 percent in various studies. Interstitial nephritis isthe most common lesion reported in primary SS which may result in to latent orovert tubular dysfunction. Clinical presentation can be distal renal tubularacidosis, nephrocalcinosis, nephrogenic diabetes insipidus or even sometimesproximal renal tubular acidosis or fanconi syndrome.

Interstitial nephritismost of the times occurs in conjunction with distal renal tubular acidosis butdRTA can be present in some patients in spite of normal renal histopathologicalfindings. Exact mechanism of dRTA is not known till date but there are manypublished articles featuring complete absence of the H-ATPase pump and anionexchanger 1 (AE1) in the intercalated cells of the collecting tubulesthat is largely responsible for distal proton secretion. High levels ofanticarbonic anhydrase antibodies affecting the functioning of carbonicanhydrase in collecting ducts have been found in few occurrences.  Literature search revealed fewcases of flaccid hypokalemic quadriparesis secondary to distal renal tubularacidosis unmasking the diagnosis of Sj?gren’s syndrome. But flaccid hypokalemicparaperesis without sicca symptoms secondary to sj?gren’s syndrome is notreported. Hypokalemic paraparesis is a rare entity in theconsideration of acute flaccid paraplegia.

 A high index of clinical suspicion and methodicalapproach are required in order to achieve the final diagnosis contributing tohypokalemia. Missing the diagnosis can contribute to recurrent episodes ofhypokalemia and eventually respiratory arrest. The frequencyof anti-Ro/SSA and anti-La/SSB antibodies has varied between studies, butgenerally 60 to 80 percent of patients of primary SS exhibit one or both ofthese auto-antibodies.

ACR-EULAR sponsored classification criteria for SS hasgiven weighted score of 3 if these positive antibodies were found. But thereare no such literature featuring the sensitivity and specificity of these testsfor SS in the absence of classical sicca symptoms. Using the ACR-EULARclassification criteria in the absence of dry symptoms  to diagnose SS would be inappropriate. Thiscriteria is materialized with the intent to be used in research trials ofemerging immunotherapy against SS.

   Like our case,a high index of suspicion and proper methodical approach is necessary todiagnose the root cause of hypokalemic paralysis unmasking Sj?gren’s disease.          References:1.