ESPE Abstracts (2015) 84 P-3-681

A Case of Vitamin D Deficient Rickets Showing Resistance to the Treatment of Active Vitamin D: Severe Calcium Deficiency Cause Vitamin D Resistance

Hiroyuki Tanakaa,b, Kosei Hasegawab, Moe Takatsukaa, Chika Okaharaa, Yoshie Noguchia, Tsutomu Takataa & Kazuo Oguraa

aOkayama Saiseikai General Hospital, Okayama, Japan; bOkayama Unversity Hospital, Okayama, Japan

Case presentation: A 2-year-boy was referred tour hospital for the rickets. He was the first son between non-consanguineous parents and fed with breast milk. But after weaning, he was avoided from taking egg, dairy products including cow’s milk. He was also suffered from developmental delay and had strong food preference. He could take only two kinds of foods, steamed rice and soy bean product, tofu. X-ray findings showed typical rachitic change on long bone metaphysis. Laboratory findings showed hypocalcaemia, hypophosphatemia, increase ALP activity (4595 IU/l), and increased intact PTH (729 pg/ml). 25 Hydroxyvitamin D was 13.2 ng/ml. From these results, vitamin D deficient rickets due to restricted food intake was diagnosed. After diagnosis, 2.5 μg/day of alphacalcidol was started. Although serum calcium and phosphorus levels were normalized, high PTH and ALP activity had not been corrected even by increased amount of alphacalcidol up to 8 μg. Genetic analysis of vitamin D receptor could not show any mutations. Functional analysis of VDR using 1,25 dihydroxyvitamin D3 induced 24 hydroxylase mRNA in the patient’s peripheral lymphocytes could not show any differences between patient and control. Although, his serum calcium levels were normal, his oral calcium intake seemed to be less than 100 mg/day. Then we added 1 g of calcium lactate. After this treatment, his PTH and ALP activity were improved rapidly. 4 months treatment of calcium lactate and small amount of active vitamin D almost completely cured rickets.

Conclusion: In conclusion, severe calcium deficiency induces vitamin D resistance in vitamin D deficient rickets. In the mechanism of the resistance the severe secondary hyperparathyroidism due to severe calcium deficiency may play an important role but detail mechanism should be unveiled.

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