Hypocalcemic rickets

Hypocalcemic rickets (Orphanet code 289103) is a group of rare metabolic bone disorders characterized by defective bone mineralization due to low levels of calcium in the blood (hypocalcemia). This category encompasses forms of rickets caused by disturbances in calcium homeostasis, including vitamin D-dependent rickets (also known as pseudovitamin D deficiency rickets) and other conditions where impaired vitamin D metabolism or action leads to insufficient intestinal calcium absorption. The resulting hypocalcemia triggers secondary hyperparathyroidism, which further disrupts phosphate and calcium balance in the body. The disease primarily affects the skeletal system, leading to characteristic features of rickets in children such as bowing of the legs, widening of the wrists and ankles, delayed fontanelle closure, growth retardation, and skeletal deformities. Affected individuals may also experience muscle weakness, hypotonia, tetany, and seizures due to low serum calcium levels. Dental abnormalities including enamel hypoplasia and delayed tooth eruption are also commonly observed. Radiographic findings typically show widened, frayed, and cupped metaphyses with generalized osteopenia. Treatment depends on the specific underlying cause. For vitamin D-dependent rickets type 1 (caused by 1-alpha-hydroxylase deficiency), treatment involves supplementation with active vitamin D (calcitriol) and calcium. For vitamin D-dependent rickets type 2 (caused by vitamin D receptor defects), high-dose calcitriol and calcium supplementation are used, though some patients with receptor mutations may be resistant to vitamin D therapy and require prolonged intravenous calcium infusions. Early diagnosis and appropriate treatment can significantly improve skeletal outcomes and prevent long-term complications.

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