Hypokalemic Paralysis Leading to Respiratory Failure: An Unusual Presentation of Sjogren’s Syndrome

Abstract

Sjogren’s Syndrome (SS) is a chronic multisystemic autoimmune inflammatory disorder with predominant exocrine gland involvement resulting in dryness of the eyes and mouth. Among extra glandular manifestations, renal involvement is commonly seen, which can be in the form of Renal Tubular Acidosis (RTA). SS may at times present as mild hypokalaemia with distal RTA but severe hypokalemia resulting in respiratory failure is rare. Here we report a case of twenty-five-year-old female presenting in emergency room with flaccid quadriparesis and hypercapnic respiratory failure. Further evaluation revealed hypokalemia (Potassium (K+) 1.6mmol/L) with distal renal tubular acidosis along with a background of primary Sjogren’s Syndrome. We illustrate that the possibility of Sjogren’s Syndrome should be considered in a young female who present with rapidly progressive weakness, hypokalemia and distal renal tubular acidosis with respiratory failure.

Keywords: Hypokalemic Flaccid Paralysis; Distal renal tubular acidosis; Sjogren’s syndrome; Respiratory failure

Abbreviations

ABG: Arterial Blood Gases; ESSDAI: EULAR Sjogren’s Syndrome Disease Activity Index; HPP: Hypokalemic Periodic Paralysis; RTA: Renal Tubular Acidosis; SS: Sjogren’s Syndrome; TTKG: Trans Tubular Potassium Gradient

Introduction

Hypokalemic Periodic Paralysis (HPP) is a rare type of periodic paralysis, with a prevalence of 1 in 100,000 population [1-4]. HPP may be familial with autosomal dominant or acquired inheritance. HPP is usually presented with acute onset of generalized weakness, proximal more than the distal. RTA in SS is usually mildly symptomatic, which is observed in up to 25% of patients [2]. Potassium concentrations less than 2mEq/L should suggest a secondary cause of hypokalemic paralysis, such as that seen in some cases of distal RTA but respiratory failure in these patients is quite rare. The potassium levels remain normal between the acute attacks in primary HPP but is at lower level in secondary HPP. The patient in this case report presented to emergency room with respiratory failure and inability to move all four limbs, which is a rare condition, associated with Sjogren’s syndrome.

Case Presentation

A 25yr old female with no known comorbidities was brought to the Emergency Room (ER) with complaints of sudden onset of weakness in all four limbs. There was a history of fall from bike three days back. She developed swelling in ankle following the fall, no bony injury was reported and there was no loss of consciousness or seizures. She was advised analgesics (Diclofenac 75mg BD for 3 days) and steroid (Deflazacort 30mg once daily for 3 days) by a local practitioner. The patient slept at 10 PM in night with no weakness and woke up in Morning with a difficulty in moving all the extremities. Initially patient was taken to a local hospital where MRI brain & spine was done and found out to be normal. In view of her respiratory distress, she was intubated and referred to a Tertiary Care Centre.

On arrival to ER, the patient was intubated and sedated, but arousable on verbal command. She was hemodynamically stable, not on any vasopressors. Neurological examination revealed lower motor neuron lesion with flaccid paralysis, power of 2/5 in upper limbs and 1/5 in lower limbs, neck flexors and extensors 0/5, deep tendon reflexes absent and bilateral plantar reflex was mute. The patient was shifted to ICU for further management. In ICU, point of care testing Arterial Blood Gas (ABG) analysis showed pH 7.06, PaO₂ 162mmHg on FiO₂ 0.4, PaCo₂ 60mmHg, Bicarbonates 13.8mmol/L, Sodium 136mmol/L, Potassium 1.6mmol/L, Chloride 110mmol/L with normal anion gap metabolic acidosis along with respiratory acidosis. Her random blood sugar was 346 mg/dl and urine ketones were negative. Fluid resuscitation was done in ICU using ringer lactate along with i.v. potassium chloride supplementation. The serum K+ level was achieved more than 3.5mmol/L in next 24 hours. The patient’s symptom improved drastically, she regained power of 5/5 with sustained neck holding for more than five seconds. The patient was extubated next day. Further investigations were performed to elucidate the etiology of hypokalemia (Table 1). In the absence of any history of gastrointestinal loss or diuretic use, the possibility of RTA was suspected as a probable cause of normal anion gap metabolic acidosis. Urinalysis revealed pH 6.0, positive urinary anion gap (59mmol/L) and Trans Tubular Potassium Gradient (TTKG) of 17, which further consolidated our diagnosis of distal RTA [3]. After extubation, the patient gave the history of dryness in eyes and mouth for last 1yr with occasional joint pains. After ruling out other causes of dryness, the possibility of SS was considered and the patient was further evaluated. Shimmers test result showed 4mm tear flow at 5min and antibodies to Sjogren’s Syndrome A (SSA Ro), Sjogren’s Syndrome B (SSB La) were strongly positive. The working diagnosis of Sjogren’s Syndrome was made based on recently developed American College of Rheumatology/European League against Rheumatism (ACR-EULAR) classification criteria for primary Sjogren’s syndrome [5]. The final diagnosis of hypokalemic paralysis with distal RTA with Sjogren’s syndrome was made. At the time of discharge, the patient was started on oral potassium citrate, artificial tears and advised for oral hygiene. On further follow-up, she has been symptom free with no further episode of hypokalemia.

  

    
Complete Blood Picture
    
Hb - 11.2g/dl, TLC -    17×109/L, Platelets - 312×109/L 
  
  

    
Serum Electrolytes 
    
Sodium - 136mmol/L,    Potassium - 1.6mmol/L, Chloride - 110mmol/L 
  
  

    
Serum Osmolality 
    
315mosm/kg 
  
  

    
Urinalysis 
    
pH - 6.0, urinary Na+ -    35mmol/L, K+ - 37mmol/L, urine chloride - 13mmol/L, urine    osmolality - 420mosm/kg 
  
  

    
Urinary Anion Gap 
    
59mmol/L (positive) 
  
  

    
TTKG
    
17 (Suggestive of renal    loss of potassium) 
  
  

    
Thyroid Function Tests
    
Within normal limits
  
  

    
Kidney Function Tests
    
Urea - 49mg/dl,    Creatinine - 1.19mg/dl 
  
  

    
Viral Markers 
    
HIV - negative, HBsAg -    negative, Anti-HCV – negative 
  
  

    
Autoimmune Profile 
    
ANA positive 
  
  

    
Anti-SS-a strongly    positive 
  
  

    
Anti -SS-b strongly    positive 
  
  

    
Schrimmers Test
    
4mm for 5min in both eyes (<10mm suggestive of    dry eyes)
  
  

    
MRI Brain & Spine
    
No abnormalities detected
  
  

    
Nerve Conduction Study
    
Normal
  
  

    
Ultrasound Abdomen
    
No evidence of nephrocalcinosis
  

Table 1: Investigations of the patient.