|Year : 2016 | Volume
| Issue : 1 | Page : 56-58
A case report of distal RTA presenting as hypokalaemic periodic paralysis in young male
Pulin Gupta, Vikas T Talreja, MS Dhananjay, Sakshi Mittal
Department of Medicine, Dr. Ram Manohar Lohia Hospital, New Delhi, India
|Date of Web Publication||21-Jan-2016|
Vikas T Talreja
GH-13/SFS Flat Number 886, Paschim Vihar, New Delhi - 110087
Source of Support: None, Conflict of Interest: None
A 21-year-old normotensive male presented with acute onset flaccid paralysis with the history of a similar episode a few months back. Clinical and laboratory evaluation revealed lower motor neuron type of flaccid quadriparesis with hypokalaemia, normal anion gap metabolic acidosis, bicarbonaturia, and transtubular potassium concentration gradient (TTKG) more than 7. Subsequently urine acidification test (by NH4CI challenge test) was done and diagnosis of distal renal tubular acidosis was established. The patient responded to conservative management (Sohl's solution).
Keywords: Distal RTA, hypokalemic periodic paralysis, metabolic acidosis with normal anion gap, renal tubular acidosis, SOHL solution
|How to cite this article:|
Gupta P, Talreja VT, Dhananjay M S, Mittal S. A case report of distal RTA presenting as hypokalaemic periodic paralysis in young male. Muller J Med Sci Res 2016;7:56-8
|How to cite this URL:|
Gupta P, Talreja VT, Dhananjay M S, Mittal S. A case report of distal RTA presenting as hypokalaemic periodic paralysis in young male. Muller J Med Sci Res [serial online] 2016 [cited 2020 May 26];7:56-8. Available from: http://www.mjmsr.net/text.asp?2016/7/1/56/174650
| Introduction|| |
Distal-renal tubular acidosis (dRTA) is a non-uremic syndrome of defective urinary acidification. It is characterized by presence of hypokalaemia, normal blood pressure, and normal anion gap metabolic acidosis, alkaline urine, inability to acidify urine pH <5.5, nephrocalcinosis, and features of rickets. Primary Drta can be inherited, but most cases are sporadic. An inherited case may be autosomal dominant or autosomal recessive form. Secondary causes are Sjögrens syndrome, amphotericin B toxicity, chronic active hepatitis, and SLE. The treatment required is alkali administration in the form of Sohl's solution in doses 0.5 to 2 ml/kg in 4-6 divided doses per day. We report a case of a 21 year-old male presenting with periodic acute onset flaccid quadriparesis with a diagnosis of d-RTA after series of investigations.
| Case Report|| |
A 21 year old student boy was admitted with acute onset quadriparesis evolving over a period of 24 hours reaching up to the extent that he could only sit or stand with adequate support. He had a similar episode two months back which was preceded by diarrhea and dehydration with hypokalaemia persisting even long after resolution of the diarrhea. On assessment of the previous records, it was revealed to be an episode of hypokalaemia leading to quadriparesis, recovered with oral KCl supplementation and discharged as hypokalaemic periodic paralysis with the advice to take Oral KCl. But this time there was no history of diarrhea. General physical examination was completely normal. No features suggestive of thyrotoxicosis were present. Nervous system examination revealed normal higher functions, cranial nerves, sensory system, bladder and bowel, and cerebellar functions. Motor examination revealed normal muscle bulk with hypotonia. Muscle power of upper limb was 4/5 and lower limb was 3/5; deep tendon reflexes were present but diminished, and plantars were bilaterally flexor. Investigation showed Hb −11.2 gm%, TLC −8,700/cmm (neutrophils −72%, lymphocytes −22%, eosinophils −4%), MCH −28.6 pg/cell, MCHC - 31.4 gm/dl, MCV −91 fL. RBS was 108 mg/dl, CPK −303 U/L, Na+ −135 mmol/ l, K+ −2.3 mmol/l, Ca2+ −3.8 mg/dl, Mg2+ −2.8 mg/dl (normal −1.5 to 2.6). Kidney function test were normal, blood urea = 20 mg/dl, s.creatinine = 0.8 mg/dl and uric acid = 3.5 mg/dl. ECG-prolonged PR interval, T-wave flattening and U wave. ABG performed: pH −7.38, pO2 −102 mmHg, pCO2 −20 mmHg, HCO3 −11.4 meq/l, Na+ −142 meq/l, K+ −2.6 meq/l, Ca2+ −120.2 meq/l, anion gap −10.4, plasma osmolality −302.5 mOsm/kg. The ABG report showed a combination of metabolic acidosis with hypokalaemia. This condition is usually found in two possible conditions either due to GI loss or RTA. As there was no history or GI loss this time, we strongly suspected RTA. Other investigations included ANA-negative, fT3 −3.58 pg/ml, fT4 −7.2 mcg/dl, TSH −1.59 IU/ml. 24 hours urine total volume −3,180 ml, K+ excretion −73.3 meq/24 hrs., i.e., 23.27 meq/l. Osmolality was 436.7 mOsm/kg and pH 7. Trans-tubular potassium gradient (TTKG) was 6.2. USG did not reveal any nephrocalcinosis. In the meantime, the patient was treated with oral potassium supplementation and patient dramatically improved. To confirm our diagnosis after stabilisation of the patient, we opted for an oral NH4Cl challenge test. UTI was ruled-out beforehand by urine microscopy and culture. NH4Cl was given orally at doses of 0.1 gm/kg with fruit juice.
Urine pH was subsequently recorded as follows:-
1 st hour −6.69
2 nd hour −6.19
3 rd hour −6.63
4 th hour −6.1
5 th hour −6.17
ABG - 2 nd hour
HCO3 −9.9 meq/l
Base excess −14.5
Na+ −133 meq/l, K + −2.4 meq/l
ABG −4 th hour
HCO3 −10.8 meg/l
Base excess −13.7 mmol/l
Na+ −139 meq/l, K+ −2.4 meq/l, Cl −118 mmol/l
Therefore, the urine pH did not decrease below 5.5 in spite of plasma HCO3 being persistently below 20 meq/l. So our diagnosis of dTRA (type 1) was confirmed. Treatment with Sohl's solution (Na-citrate 500 mg, K-citrate 550 mg, and citric acid 334 mg/5 ml) was started. 1 ml of this solution is equivalent to 1 meq of Na+, 1 meq of K+ and 2 meq of HCO3. It was started at a dose of 1 mmol/kg per day in divided doses. After one week of starting therapy serum K+ was 4 meq/l, Cl- - 102 meq/l, pH - 7.4, and HCO3 - 23.8 meq/l. ECG at discharge was normal. In follow-up, the patient is doing well.
| Discussion|| |
Renal tubular acidosis (RTA) is a medical condition that involves an accumulation of acid in the body due to a failure of the kidneys to appropriately acidify the urine either by failure to recover sufficient (alkaline) bicarbonate ions from the filtrate in the early portion of the nephron (proximal tubule) or by insufficient secretion of (acid) hydrogen ions into the latter portions of the nephron (distal tubule).  Distal RTA (dRTA) is the classical form of RTA, characterized by a failure of acid secretion by the alpha intercalated cells of the cortical collecting duct. This leads to an inability to acidify the urine to a pH of less than 5.5. The clinical features of dRTA include1: Normal anion gap metabolic acidosis/acidaemia, hypokalaemia, urinary stone formation (related to alkaline urine, hypercalciuria, and low urinary citrate),  nephrocalcinosis (deposition of calcium in the substance of the kidney) and bone demineralization (causing rickets in children and osteomalacia in adults).  Our patient had low pco2 which can be explained by chronic metabolic acidosis due to bicarbonaturia leading to hyperventilation for removal of excess acid. The diagnosis of dRTA can be made by the observation of a urinary pH of greater than 5.5 in the face of a systemic acidaemia (usually taken to be serum bicarbonate of 20 mmol/l or less). The test usually performed is the short ammonium chloride test,  in which ammonium chloride capsules are used as the acid load. Secondary causes include: Autoimmune disease (e.g., Sjφgrens syndrome),  mutations of Band 3,  subunits of the apical proton pump vH+-ATPase, ,, renal transplantation, sickle cell anaemia, toxins - including ifosfamide,  toluene,  lithium carbonate  and amphotericin B;  and chronic active hepatitis.  On the other hand, periodic paralysis due to hypokalaemia is often due to hypokalaemic periodic paralysis, an inherited channelopathy.  Since the clinical features of both RTA type I and RTA type II can be similar, distinguishing between them can be a diagnostic challenge. These two causes of nonanion gap acidosis with hypokalemia can be distinguished relatively easily, with some laboratory testing. The easiest and most readily tested laboratory examination is the urine pH. In RTA I, the distal tubule is unable to acidify the urine and results in a urine pH that is above 5.5. RTA type II, however, has intact distal acidification which, together with an ability of the proximal tubule to reabsorb filtered bicarbonate once its concentration has fallen below its abnormally low tubular reabsorptive capacity, results in a urine pH <5.5. With these mechanisms, RTA II usually does not cause as profound a serum acidosis as RTA I. However, because the clinical manifestations of hypokalaemia are mainly muscle weakness, it may be difficult, in some cases, to discriminate between a paralytic attack of hypokalaemic periodic paralysis and an episode of weakness associated with hypokalaemia of another cause (e.g., reduced potassium intake, enhanced renal excretion, or digestive loss) requiring varied investigations.
In our case, all possible causes were excluded by appropriate investigations and diagnosis of d- RTA was established by ABG, 24-hour urinary potassium excretion, TTKG, NH4Cl challenge test. Treatment with Sohl's solution was followed by rapid recovery.
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