Hypocalcemic Disorders

Key Features

• Tetany with facial and extremity numbness, tingling, cramps, spontaneous muscle contractures, carpopedal spasm, positive Trousseau and Chvostek signs, loss of consciousness, and convulsions

• Diarrhea, prolongation of electrical systole (QT interval), and laryngospasm

• In hypoparathyroidism or pseudohypoparathyroidism (PHP): defective nails and teeth, cataracts, and ectopic calcification in the subcutaneous tissues and basal ganglia

Clinical Findings

• Prolonged hypocalcemia from any cause is associated with tetany, photophobia, blepharospasm, and diarrhea

• Symptoms of tetany include numbness, muscle cramps, twitching of the extremities, carpopedal spasm, and laryngospasm

• Tapping the face in front of the ear causes facial spasms (Chvostek sign)

• Some patients with hypocalcemia exhibit bizarre behavior, irritability, loss of consciousness, and convulsions

• Headache, vomiting, increased intracranial pressure, and papilledema may occur

• In early infancy, respiratory distress may be a presenting finding

Diagnosis

• Magnesium levels may also be low

• Measurement of urinary excretion of calcium (calcium-creatinine ratio) can assist in diagnosis and monitoring of therapy in children on calcitriol therapy

• Various skeletal changes are associated with rickets, including cupped and irregular long bone metaphyses

• Torsional deformities can result in genu varum (bowleg)

• Accentuation of the costochondral junction gives the rachitic rosary appearance seen on the chest wall

Treatment

• Administer intravenous calcium gluconate or calcium chloride at a dose of 10 mg/kg

• Intravenous calcium infusions should not exceed 50 mg/min because of possible cardiac arrhythmia

• Cardiac monitoring should be performed during calcium infusion

• Calcium supplementation should start at a dose of 50–75 mg of elemental calcium per kilogram per day divided in three to four doses

• Ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃) are the most commonly used oral vitamin D preparations

  • Cholecalciferol is slightly more active than ergocalciferol

  • Calcitriol (1,25-dihydroxy vitamin D₃) supplementation is recommended for impaired metabolism of dietary vitamin D to 25-OH vitamin D as seen in hepatic dysfunction, or to its active end product, 1,25-dihydroxy vitamin D, or impaired PTH function

  • Selection and dosage of vitamin D supplements varies with the underlying condition and the response to therapy