|Year : 2015 | Volume
| Issue : 6 | Page : 760-762
Hypokalemic periodic paralysis: Three rare secondary causes
Prasanna Eswaradass Venkatesan, Gnanagurusamy Gnanashanmugham, Ramasamy Balakrishnan, Kalidoss Ramadoss
Department of Neurology, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
|Date of Web Publication||19-Nov-2015|
Prasanna Eswaradass Venkatesan
3, Vijayarahavachari Road, Gandhi Road, Salem - 636 007, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Periodic paralysis is a rare neuromuscular disorder, related to a defect in muscle ion channels, characterized by episodes of painless muscle weakness, which may be precipitated by heavy exercise, fasting, or high-carbohydrate meals. Hypokalemic periodic paralysis may be familial (primary) or secondary. Here, we report three cases of secondary causes of hypokalemic periodic paralysis. On evaluation, case 1 had distal renal tubular acidosis (RTA) due to Sjogren's syndrome, case 2 had drug induced proximal RTA (Fanconi's syndrome) and case 3 had thyrotoxicosis. Clinician must be aware of causes of secondary PP as recognition and diagnosis can completely prevent further attacks of periodic paralysis. Each of the above case is rare, but completely treatable if diagnosed. Low dose steroids with bicarbonate replacement in case 1, stopping tenofovir in case 2 and carbimazole therapy in case 3 prevented further attacks of periodic paralysis and cardiopulmonary complications.
Keywords: Hypokalemic periodic paralysis, renal tubular acidosis, secondary periodic paralysis
|How to cite this article:|
Venkatesan PE, Gnanashanmugham G, Balakrishnan R, Ramadoss K. Hypokalemic periodic paralysis: Three rare secondary causes. Med J DY Patil Univ 2015;8:760-2
|How to cite this URL:|
Venkatesan PE, Gnanashanmugham G, Balakrishnan R, Ramadoss K. Hypokalemic periodic paralysis: Three rare secondary causes. Med J DY Patil Univ [serial online] 2015 [cited 2019 Jun 16];8:760-2. Available from: http://www.mjdrdypu.org/text.asp?2015/8/6/760/169918
| Introduction|| |
Periodic paralysis is a rare neuromuscular disorder, related to a defect in muscle ion channels, characterized by episodes of painless muscle weakness, which may be precipitated by heavy exercise, fasting, or high-carbohydrate meals. Hypokalemic PP may be familial (primary) or secondary. Important secondary causes include renal tubular acidosis (RTA), primary hyperaldosteronism, Barter syndrome, Gitelman syndrome, licorice ingestion, barium ingestion, thyrotoxicosis and GI loss [Table 1].
|Table 1: Differences between primary and secondary hypokalemic periodic paralysis|
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| Case Reports|| |
A 26-year-old female with no significant history or family history came with complaints of acute onset of weakness of all 4 limbs progressing to complete quadriplegia over few hours. On examination, she had a bilateral symmetrical flaccid quadriplegia with weakened neck muscles, diminished reflexes and normal sensations. Investigations revealed hypokalemia and metabolic acidosis and urine pH -7.0 suggestive of RTA. Investigations revealed distal RTA with high Erythrocyte sedimentation rate-93. Antinuclear antibodie profile was sent and showed strongly positive for Sjogren syndrome A (SS-A), SS-B and RO-52 [Table 2]. She was diagnosed of SSs with distal RTA. Patient was treated with intravenous potassium replacement and recovered completely by next day. She is on regular follow-up with nephrologist and has not had any similar episodes.
A 55-year-old female with HIV infection for past 7 years presented with acute onset of myalgia and muscle weakness of all 4 limbs proximal more than distal of 1-day duration. She also noted increased fatigue and polyuria over past 3 days. No history of diarrhea, neurological, renal disorders. She was on regular tenofovir, emtricitabine, azatanavir last 10 months. Deep tendon reflexes and sensory system was normal. On investigation she had hypokalemia, hyperchloremic, metabolic acidosis, hypophosphatemia, glucosuria, and proteinuria [Table 2]. Proximal RTA (Fanconi's syndrome) was suspected secondary to tenofovir. She was treated with intravenous potassium replacements, and she improved immediately in over 3 h. We stopped tenofovir, and she was followed-up for next 6 months. She was asymptomatic during this period but eventually was lost in follow-up.
The 30-year-old male came with weakness of all four limbs of acute onset. History of similar episode 6 months back which improved with IV fluid treatment in the local hospital. Now on examination patient has power 3/5 in all limbs with normal sensory and diminished deep tendon reflexes. Investigations revealed hypokalemia, normal arterial blood gas analysis and other electrolytes. Thyroid function revealed low thyroid stimulating hormone and elevated T3, T4 [Table 2]. She was treated with intravenous potassium and had a dramatic improvement the next day. She is on regular follow-up and has not had a similar episode.
| Discussion|| |
Renal tubular acidosis is a normal anion gap hyperchloremic acidosis that occurs due to nonazotemic renal acidification defect. There are 2 major types as follows [Table 3].
Case 1 was an otherwise healthy female, presented with acute onset flaccid quadriplegia and investigations revealed distal RTA. Distal RTA may be primary or more commonly secondary to paraproteinemia, medullary sponge kidney, nephrocalcinosis and autoimmune disease. Hypokalemia due to distal RTA is usually a late manifestation. However, it has been reported in <2% cases of SS as a presenting manifestation.  The systemic manifestations necessitate corticosteroids or cytotoxic agent. Our patient is presently receiving low dose of steroid and hydroxychloroquine.
Case 2 was a retroviral disease patient on treatment presented with myalgia and muscle weakness. On the evaluation, she had typical findings of proximal RTA. Heritable Fanconi syndrome includes cystinosis, galactosemia, Wilson's disease and tyrosinemia. Acquired causes include multiple myeloma, renal transplantation and medications like aminoglycosides, ifosfamide, cisplatin, tetracycline, valproic acid, cidofovir and adefovir. Tenofovir was initially introduced in the United States in October 2001 and much later in India. There are very few case reports of tenofovir induced fanconi syndrome and still fewer cases of hypokalemic periodic paralysis.  If clinicians are aware patients can be followed more closely with a urinalysis, serum creatinine, and potassium in the first 12-18 months of tenofovir therapy.
Case 3 had typical thyrotoxic periodic paralysis (TPP) characterized by muscle paralysis and hypokalemia due to a massive intracellular shift of potassium. Despite a much higher incidence of thyrotoxicosis in women, TPP predominantly affects males. Clinical features of hyperthyroidism in patients with TPP may be subtle. Severity of thyrotoxicosis does not correlate with weakness. Increased sodium-potassium ATPase pump activity and enhanced insulin response in patients with TPP are postulated to contribute to the hypokalemia. Nonselective beta-adrenergic blockers can ameliorate and prevent recurrence of the paralytic attacks. Aggressive potassium treatment may produce rebound hyperkalemia during recovery. TPP is a curable disorder that resolves when a euthyroid status is achieved. 
| Conclusion|| |
Clinician must be aware of causes of secondary periodic paralysis as recognition and diagnosis can completely prevent further attacks of periodic paralysis. , Each of the above case is rare but completely treatable if diagnosed. Low dose steroids with bicarbonate replacement in case 1, stopping tenofovir in case 2 and carbimazole therapy in case 3 prevented further attacks of periodic paralysis and cardiopulmonary complications.
| References|| |
Raskin RJ, Tesar JT, Lawless OJ. Hypokalemic periodic paralysis in Sjögren's syndrome. Arch Intern Med 1981; 141:1671-3.
Mathew G, Knaus SJ. Acquired Fanconi's syndrome associated with tenofovir therapy. J Gen Intern Med 2006;21:C3-5.
Kung AW. Clinical review: Thyrotoxic periodic paralysis: A diagnostic challenge. J Clin Endocrinol Metab 2006; 91:2490-5.
Rao N, John M, Thomas N, Rajaratnam S, Seshadri MS. Aetiological, clinical and metabolic profile of hypokalaemic periodic paralysis in adults: A single-centre experience. Natl Med J India 2006;19:246-9.
Kayal AK, Goswami M, Das M, Jain R. Clinical and biochemical spectrum of hypokalemic paralysis in North: East India. Ann Indian Acad Neurol 2013;16:211-7.
[Table 1], [Table 2], [Table 3]