Autosomal dominant hypophosphatemic rickets

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Autosomal dominant hypophosphatemic rickets (ADHR) is a rare genetic disorder characterized by rickets and osteomalacia due to renal phosphate wasting. This condition is inherited in an autosomal dominant manner, meaning a single copy of the mutated gene can cause the disorder.

Genetics

ADHR is caused by mutations in the FGF23 gene, which encodes the protein fibroblast growth factor 23. This protein plays a crucial role in regulating phosphate homeostasis. Mutations in FGF23 lead to increased activity of the protein, resulting in reduced phosphate reabsorption in the kidneys and decreased levels of active vitamin D.

Clinical Features

Patients with ADHR typically present with symptoms of rickets, such as bone pain, skeletal deformities, and growth retardation. In adults, the condition can lead to osteomalacia, which is characterized by softening of the bones, leading to fractures and bone pain. Other symptoms may include muscle weakness and fatigue.

Diagnosis

The diagnosis of ADHR is based on clinical evaluation, biochemical tests, and genetic testing. Biochemical tests typically show low serum phosphate levels, elevated levels of alkaline phosphatase, and inappropriately normal or low levels of 1,25-dihydroxyvitamin D. Genetic testing can confirm the diagnosis by identifying mutations in the FGF23 gene.

Treatment

The treatment of ADHR focuses on managing symptoms and correcting phosphate levels. This often involves oral phosphate supplements and active vitamin D analogs, such as calcitriol. Regular monitoring of serum phosphate and calcium levels is essential to avoid complications such as hypercalcemia and nephrocalcinosis.

Prognosis

The prognosis for individuals with ADHR varies. Early diagnosis and appropriate treatment can improve symptoms and prevent complications. However, some patients may continue to experience bone pain and fractures despite treatment.

See Also

• Rickets
• Osteomalacia
• Hypophosphatemia
• Fibroblast growth factor 23

External Links

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