Introduction:
In young populations, Vitamin D deficiency is typically rare due to their active lifestyles that include ample sun exposure and sufficient dietary intake of vitamin D-rich foods. Additionally, the incidence of malabsorption syndromes is relatively low in this demographic. However, with the onset of the COVID-19 pandemic, many activities have become limited to home-based settings, including schooling and reduced outdoor physical engagement, such as sports and fieldwork. We present a case of a 21-year-old Filipino male college student who complained of weakness in his bilateral lower extremities, resulting in difficulty ambulating. He was referred to the renal service due to multiple electrolyte imbalances, including hypokalemia, hypocalcemia, and hypophosphatemia. A detailed review of the patient’s medical history, along with comprehensive physical examination, laboratory tests, and diagnostic imaging, led to the diagnosis of Proximal Renal Tubular Acidosis secondary to Vitamin D deficiency.
Methods:
Results:
Case: A 21-year-old Filipino male college student was hospitalized due to weakness in his bilateral lower extremities, which resulted in difficulty with ambulation. His lifestyle during the COVID-19 pandemic involved limited sunlight exposure. He had a history of recurrent episodes of body weakness and a family history of hypokalemia associated with nephrolithiasis. Upon admission, his vital signs were stable, but muscle strength in the lower limbs was severely reduced, while sensory function and deep tendon reflexes remained normal. Initial tests indicated chronic respiratory alkalosis with concomitant high anion gap and non-anion gap metabolic acidosis, along with slightly low ionized calcium, low potassium, and inorganic phosphorus. He was treated with intravenous and oral potassium chloride, but calcium correction was not yet considered. The patient was referred to the nephrology service, where further diagnostics were requested, and the potassium chloride dosage was increased. Given the patient’s history, distal renal tubular acidosis was suspected hence, potassium citrate and sodium bicarbonate were initiated. A renal ultrasound was performed, revealing a normal sonogram of both kidneys with no noted stones. The patient also experienced carpopedal spasms and hyperventilation, with positive chvostek and trousseau’s signs. Diagnostics showed sinus tachycardia on 12-lead ECG, further decreased ionized calcium, low vitamin D, and acute respiratory alkalosis with concomitant high anion gap and non-anion gap metabolic acidosis. Calcium gluconate was administered, and the patient began treatment with calcium carbonate and initiation of colecalciferol. Despite low calcium and vitamin D levels, parathyroid hormone level was normal. Urine biochemistry showed hypercalciuria and alkaline pH. Based on the biochemical profile, an initial diagnosis of Mixed Renal Tubular Acidosis Type 3 was made (Proximal RTA from Vitamin D deficiency and Distal RTA, probably Inherited); Primary Hypoparathyroidism; and Depressive Disorder. Treatment included calcium replacements, potassium citrate, sodium bicarbonate, and colecalciferol. Hydrochlorothiazide was added for the management of hypercalciuria and hypocalcemia. Following treatment, the patient’s condition improved, leading to discharge with maintenance medications and advice for daily sun exposure. He was monitored as an outpatient, remained asymptomatic, and was eventually maintained on a Vitamin D regimen, with a final diagnosis of Proximal Renal Tubular Acidosis secondary to Vitamin D deficiency and primary hypoparathyroidism. With Vitamin D supplementation alone, electrolyte imbalances remained corrected and symptoms did not recur, confirming that Vitamin D deficiency was the primary cause of the patient’s condition.
Conclusions:
This case illustrates the role of Vitamin D deficiency in proximal renal tubular acidosis. Limited literature support Vitamin D deficiency as a potential cause of proximal RTA. Our patient showed significant clinical improvement following Vitamin D replacement therapy, suggesting that Vitamin D status should be routinely assessed in the diagnostic evaluation of proximal RTA. Addressing Vitamin D deficiency may not only alleviate the associated tubular dysfunction but also serve as an effective therapeutic approach for patients with this condition.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.