Idiopathic Distal Renal Tubular Acidosis Presenting as Polymorphic Ventricular Tachycardia

Naveed Mohsin; Javvid Muzamil Dandroo; Shabir Ahmed Rather; Firdousa Nabi

doi:10.4103/2225-1243.161441

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CASE REPORT

Year : 2015 | Volume : 2 | Issue : 3 | Page : 96-98

Idiopathic Distal Renal Tubular Acidosis Presenting as Polymorphic Ventricular Tachycardia

Naveed Mohsin¹, Javvid Muzamil Dandroo¹, Shabir Ahmed Rather¹, Firdousa Nabi²
¹ Department of Internal Medicine, SKIMS, Soura, Srinagar, India
² Department of Prosthodonsia, Govt. Dental College, Srinagar, Jammu and Kashmir, India

Date of Web Publication

24-Jul-2015

Correspondence Address:
Dr. Javvid Muzamil Dandroo
Married Hostel, Room Number F16, SKIMS, Soura, Srinagar - 190 011, Jammu and Kashmir
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/2225-1243.161441

Abstract

Renal tubular acidosis is a known clinical entity, in which type I distal renal tubular acidosis (dRTA type I), also known as classical dRTA, is second most common type after dRTA type IV. We report 21-year-old female presenting as polymorphic ventricular tachycardia (VT), which on evaluation was found to have the type I dRTA with idiopathic etiology. Polymorphic VT as presentation of type I dRTA has not been reported in the literature in human beings so far but has been reported in animal models.

Keywords: Distal renal tubular acidosis, fractional excretion of bicarbonate, generalized tonic clonic seizures, ventricular tachycardia

How to cite this article:
Mohsin N, Dandroo JM, Rather SA, Nabi F. Idiopathic Distal Renal Tubular Acidosis Presenting as Polymorphic Ventricular Tachycardia. J Integr Nephrol Androl 2015;2:96-8

How to cite this URL:
Mohsin N, Dandroo JM, Rather SA, Nabi F. Idiopathic Distal Renal Tubular Acidosis Presenting as Polymorphic Ventricular Tachycardia. J Integr Nephrol Androl [serial online] 2015 [cited 2023 May 28];2:96-8. Available from: http://www.journal-ina.com/text.asp?2015/2/3/96/161441

Introduction

Renal tubular acidosis is a known clinical entity, with type I distal renal tubular acidosis (dRTA type I) the second most common type. This entity is commonly seen in children and mostly diagnosed in early age group. dRTA type I is the classical form of RTA, was first described among all RTA. ^[1] dRTA type I is characterized by a failure of H ⁺ secretion into the lumen of the nephron by the alpha intercalated cells of the medullary collecting duct of the distal nephron. ^[2],[3],[4] This failure of acid secretion may be due to a number of causes, and it leads to an inability to acidify the urine to a pH of <5.5. ^[5],[6] Because renal excretion is the primary means of eliminating H ⁺ from the body, there is consequently a tendency toward acidemia. There is an inability to excrete H ⁺ while as K ⁺ cannot be reclaimed by the cell, leading to acidosis and hypokalemia.

Etiologically, many conditions can present or cause RTA. In dRTA type I, Sjogren's syndrome is most common secondary etiology. Other conditions are giving rise to dRTA type I are systemic lupus erythematosus, thyroiditis, primary biliary cirrhosis, chronic active hepatitis, analgesic use, hyperthyroidism, hyperparathyroidism, and many more.

Most common presentation among children is growth retardation. Other presentations are Confusion or decreased alertness, fatigue, increased breathing rate, kidney stones, nephrocalcinosis, osteomalacia, rickets, muscle weakness, bone pain, decreased urine output, Increased heart rate or irregular heartbeat, muscle cramps, pain in the back, flank, or abdomen, and Skeletal abnormalities.

In young adults and elderly, dRTA type I present with myalgia and arthralgia, ^[7] arrhythmia, mostly ventricular premature contraction (VPC's), osteomalacia, hypokalemic weakness, respiratory muscle weakness, and confusion. Our patient presented with multiple episodes of ventricular tachycardia (VT) with spontaneous terminations.

Case Report

A 21-year-old married female with no significant past medical history, presented with multiple brief unresponsive spells with abnormal body movements (generalized tonic-clonic seizures [GTCs]) lasting between 2 and 5 min for last 2 years. Patient was evaluated twice before for possible cause of seizures and each time magnetic resonance imaging (MRI) brain and electroencephalogram (EEG) were done; both were reported as normal. Patient was diagnosed as conversion disorder and was put on psychiatric follow-up. However, patient continued to have similar spells. Presently she came to our emergency department with similar multiple brief unresponsive spells with abnormal body movements (GTCs) for few minutes with immediate regaining of consciousness. There was no other significant history. On examination, patient was conscious, pulse 100 per minute and irregular, blood pressure 110/80 mmHg, and the rest of clinical examination was unremarkable.

On evaluation her hemoglobin was 11.5 g/dL, leucocyte count 6400/mm ³ , erythrocyte sedimentation rate 21 mm for the 1 ^st h, random blood sugar 110 mg/dL, blood urea nitrogen 12 mg/dL, serum creatinine 0.9 mg/dL, uric acid 3.2 mg/dL, aspartate aminotransferase 44 IU/L, ALT 43 IU/L, alkaline phosphatase 130 IU/L, creatine kinase 190 IU/L, bilirubin 0.6 mg/dL, albumin 3.6 mg/dL, calcium 8.9 mg/dL, and phosphorous 1.9 mg/dL. Blood gas analysis revealed pH 7.28 (n = 7.35-7.45), serum potassium 1.6 (n = 3.5-5.0) mEq/L, serum sodium 140 (n = 135-148) mEq/L, pCO ₂ 30 (35-45) mmHg, pO ₂ 90 (80-100) mmHg, [HCO ₃ ]⁻ 10.5 mEq/L, chloride 120 mEq/L and an anion gap of 11.1 suggesting hyperchloremic normal anion gap metabolic acidosis. Electrocardiogram (ECG) [Figure 1] showed polymorphic VPC's with frequent bigeminy pattern. Patient was put on continuous ECG monitoring which showed occurrence of intermittent polymorphic VT [Figure 2], consistent with unresponsive spells.

Figure 1: Electrocardiogram — showing bigeminy pattern with alternating ventricular premature contraction and normal sinus beat

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Figure 2: Electrocardiogram — showing polymorphic ventricular tachycardia self-terminated

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Patient was given intravenous potassium, and magnesium sulfate, and her repeat serum electrolytes normalized. Further evaluation was carried out to look for the cause of VT. In the meantime, patient reverted to sinus rhythm and had no more similar spells.

Echocardiography was normal. MRI brain and awake EEG were normal.

Patient was evaluated for hyperchloremic normal anion gap metabolic acidosis and following parameters were checked. Urinary pH was 6.0, and urinary anion gap was 60 mEq/L with urinary sodium (U _Na ⁺ ) of 70.0, chloride (UCl⁻ ) of 50 and potassium (Uk ⁺ ) of 40. Urine for glucose and amino acids were negative. Bicarbonate loading test was carried out to differentiate from proximal metabolic acidosis. Patient received 7.5% soda bicarbonate intravenous at the rate of 2 mL/min for 2 h till urinary PH reached to 7.5, which was confirmed thrice. Urinary [HCO3]⁻ was 75 mEq/L, urinary creatinine 50 mg/dL, serum creatinine 1.0 mg/dL of and serum [HCO3]⁻ of 35, with fractional excretion of bicarbonate [FEHCO3⁻ ] of 4.2%.

Further investigations were carried out to look for etiology of dRTA. Ultrasound abdomen showed nephrolithiasis [Figure 3]. Her 24-h urinary protein was 280 mg, serum Vitamin D level was 21.86 (normal 9-47) ng/mL, serum parathormone level 54.0 (normal 9-55) pg/mL, thyroid stimulating hormone 5.0 (normal 0.6-5.5) μU/mL, T4 10 (normal 5-12) μg/dL and antinuclear antibody was negative.

Figure 3: Ultrasonography — showing nephrolithiasis

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Patient was put on supplemental soda bicarbonate and potassium at the time of discharge. There were no such episodes of unresponsiveness after admission and multiple ECG's were normal.

Finally, diagnosis of idiopathic type I dRTA was made presenting as polymorphic VT. The cause of VT was prolonged severe hypokalemia and acidosis.

Discussion

Renal tubular acidosis was first described in 1935 by Lightwood and 1936 by Butler et al. in children. ^[1],[8] Baines et al. first described it in adults in 1945. ^[9] A normal anion gap pattern is commonly found in patients with both acute and chronic metabolic acidosis. Between 19% ^[10] and 41% ^[11] of patients in intensive care units with acute metabolic acidosis and 20-55% of individuals with chronic uremic acidosis have a nongap pattern. ^[12],[13] This pattern can originate from a number of pathophysiologic mechanisms; therefore, determination of its cause can be challenging.

Among all types of RTA, type IV is most common, followed by the type I dRTA. The causes of type I dRTA in adults are autoimmune disorders (Sjogren's syndrome, rheumatoid arthritis), hypercalciuria, recreational toluene sniffing and drug-induced (amphotericin B) and marked volume depletion and many more. In children, type I RTA is most often a hereditary condition. Genetic mutations in the chloride-bicarbonate co-transporter and in the apical H ⁺ -ATPase have been identified. ^{[14],[15],[16]}

Renal tubular acidosis has diverse presentations. In children, it presents mostly with growth failure and in young adults and elderly, dRTA type I present with myalgia and arthralgia, arrhythmia, osteomalacia, hypokalemic weakness, respiratory muscle weakness, confusion, etc. Our patient presented with multiple episodes of nonsustained polymorphic VT. Adults can present with arrhythmias in the form of VPC's, APC's, blocks and fibrillations. All arrhythmias are likely due to hypokalemia and acidosis. ^[17] In our review of the literature, till date there is no report of the type I RTA with polymorphic VT in humans but animal (horse) models do have reports. ^[18]

Hence, in the light of the present patient every unresponsive spell is not seizure and cardiac arrhythmia should be definitely ruled out when a patient gets multiple brief self-terminating unresponsive spells. It is also important to look for RTA as a possibility if one presents with cardiac arrhythmias, hypokalemia, and metabolic acidosis.

References

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