Repeated hypocalcemia in a patient with “Hikikomori” following veganism

In some cases, hypocalcemia may lead to fatal outcomes. A 33-year-old woman who had been withdrawing from society (Hikikomori) and followed a vegan diet, arrived at the emergency department (ED) due to numbness and stiffness. She has been to another ED several times for hypocalcemia. Each time, intravenous calcium infusions improved her symptoms, and she went home. Her doctor prescribed calcium supplementation; however, she often experienced symptoms of hypocalcemia. On arrival at our ED, Trousseau’s and Chvostek's signs were observed. Her corrected calcium levels (cCa) and ionic calcium levels (iCa) were 7.0 mg/dL and 3.0 mg/dL, respectively. Intravenous calcium was administered, following which her symptoms improved by day 2. Subsequently, her 1,25(OH)2-vitamin D and 25-OH vitamin D levels decreased to 8 pg/mL and < 4 ng/mL (below the measurement sensitivity), respectively. We diagnosed hypocalcemia due to inadequate calcium absorption caused by vitamin D deficiency. Therefore, she was prescribed active vitamin D supplementation, in addition to calcium supplementation, which led to resolution of hypocalcemia symptoms. In our patient, hypocalcemia was thought to have been caused by inadequate calcium intake. However, our data revealed that her repeated hypocalcemia symptoms were due to vitamin D deficiency, caused by a lack of sunlight. It is important that patients with "Hikikomori" who follow a vegan diet and are thought to have low calcium intake and sunlight exposure, take active vitamin D and calcium supplementation, to prevent hypocalcemia. Calcium absorption; Vitamin D deficiency; Lack of sunlight; Hikikomori; Vegan.