A Case of Proximal Renal Tubular Acidosis Accompanied by Vitamin D Deficient Rickets

비타민 D 결핍성 구루병에 동반된 근위 신 세뇨관성 산증 1례

In the clinical state of vitamin D deficiency, it is possible that associated phosphate depletion, parathyroid hormone excess, and hypocalcemia may all depress the proximal tubular reabsorption of bicarbonate, in addition to abnormal skeletal modeling or remodeling, Although nutritional rickets is considered a rare disease in developed countries nowadays, cases of vitamin D deficient rickets caused by various unhealthy lifestyles such as insufficient exposure to sunlight, breast feeding infants without giving vitamin D supplements, unbalanced vegetarian diets of breast feeding mothers, low-birth weight, and maternal deficiency of vitamin D or calcium are increasing. Here, we present the case of an 8 month old girl, who was completely breastfed without any weaning diet or infant vitamin supplements. She visited our emergency room with hypocalcemic seizure and subsequently was diagnosed with vitamin D deficient rickets accompanied by overt bone changes and proximal renal lobular acidosis. After intravenous(IV) and oral calcium replacement therapy(IV calcium gluconate injection 1 mEq/kg/day for 6 days, 2 mEq/kg/day for 4 days followed by oral calcium gluconate administration 4 g/day for 3 days) with vitamin D supplement(Alfacalcidol 0.5 mcg/day) during admission, serum calcium level was normalized with clinical improvement. Oral sodium bicarbonate(0.6 g/day) was administered from the $2^{nd}$ hospital day for 2 weeks, which normalized the serum bicarbonate(measured by $tCO_2$) level. Calcium and vitamin D replacement were continued for 2 weeks and 3 months each. After discontinuing medications, follow up laboratory findings showed good maintenance of serum calcium, alkaline phosphate and bicarbonate levels with complete improvement of bone X-ray findings.

최근 들어 모유 단독 수유의 장기화 및 잘못된 식이 제한 등으로 인한 비타민 D 결핍성 구루병의 발병이 점차 증가하고 있는 시점에서, 비타민 D 결핍성 구루병 및 이와 동반된 저칼슘혈증성 경련에 대한 예는 다소 보고된 바 있으나, 비타민 D 결핍으로 인해 골 병변 뿐 아니라 저칼슘 혈증, 부갑상선 기능 항진증, 나아가 신세뇨관성 산증까지 초래한 예는 보고된 바가 없었다. 저자들은 8개월간 모유 단독 수유만 유지하던 중 저칼슘혈증성 경련을 주소로 내원하여 골 병변을 동반한 비타민 D 결핍성 구루병과 부갑상선 항진 및 근위 세뇨관성 산증을 진단 받은 후, 적절한 칼슘, 비타민 D, 중탄산염 투여 후 완전히 회복된 환자의 1례를 경험하였기에 보고하는 바이다.