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Vitamin D-Binding Protein Deficiency and Homozygous Deletion of the GC Gene

By April 2, 2019No Comments

A 58-year-old woman with debilitating ankylosing spondylitis who was born to consanguineous parents was found to have an apparent severe vitamin D deficiency that did not respond to supplementation. Liquid chromatography-tandem mass spectrometry showed the absence of circulating vitamin D-binding protein, and chromosomal microarray confirmed a homozygous deletion of the group-specific component (GC) gene that encodes the protein. Congenital absence of vitamin D-binding protein resulted in normocalcemia and a relatively mild disruption of bone metabolism, in this case complicated by severe autoimmune disease.