Bone Abstracts

Background: Hereditary pseudovitamin D-deficiency rickets, also known as vitamin D-dependent rickets type I, with an autosomal recessive inheritance, is caused by mutations in CYP27B1. It is characterized clinically by hypotonia, weakness, growth failure, and hypocalcemic seizures in early infancy. The patients also have hypocalcemia, radiologic findings typical of rickets, elevated serum parathyroid hormone concentrations, and generalized aminoaciduria. We present follow-up of a case with a novel mutation including improvement of disease monitored by computed tomography of the bones and lungs. Adequate treatment resulted in a normalized lung function.

Presenting problem: Our patient is the boy from consanguineous healthy caucasian parents. He was diagnosed with VDDR at age 3 years 8 months after he was admitted in Intensive Care Department (ICD) with respiratory insufficiency and started invasive lung ventilation. Earlier he was diagnosed with pulmonary hypertension and dilated cardiomyopathy. During examination growth failure and hypotonia were described. Diagnose was based on the hypocalcemia, hypophosphatemia, elevated serum parathyroid hormone concentration and radiological findings. During the genetic testing disease was confirmed. In CYP27B1 gene was founded a homozygous mutation NM_000785: exon1: c.C90A: p.Y30X that is not described in HGMD. Considering the exists of rickets, the boy was suspected having chronic lung disease.

Clinical management: A patient with chronic respiratory failure was treated with oxygen supplementation with therapy for underlying disease. We started treatment with active form of vitamin D and phosphate. The child was transferred to constant oxygen support at home. After 1 year of high dose active vitamin D treatment the patient is self-breathing without oxygen supplementation during all the day and night.

Discussion: The development of chronic lung disease in vitamin D-dependent rickets has combined reasons of both chest volume reduction and effect of the vitamin D on pulmonary cell biology and immunity with impact on inflammation. Despite the fact that respiratory manifestations were described earlier, in this case, important questions are needed about the timeliness of diagnosis, the risk of complications and treatment.

Disclosure: The authors declared no competing interests.