Marsden Nyhan Sakati syndrome
Overview
A very rare syndrome characterized mainly by reduced parathyroid hormone level, low growth hormone level and other minor abnormalities.
Symptoms
* Low parathyroid hormone level * Low growth hormone level * Developmental delay * Low blood calcium level
Causes
Hypoparathyroidism may be acute or chronic and is classified as idiopathic or acquired. The acquired form may also be reversible. Idiopathic hypoparathyroidism may result from an autoimmune genetic disorder or the congenital absence of the parathyroid glands. Acquired hypoparathyroidism commonly results from accidental removal of or injury to one or more parathyroid glands during thyroidectomy or other neck surgery; rarely it results from massive thyroid irradiation. It may also result from ischemic infarction of the parathyroids during surgery or from hemochromatosis, sarcoidosis, amyloidosis, tuberculosis, neoplasms, or trauma. An acquired, reversible hypoparathyroidism may result from hypomagnesemia-induced impairment of hormone synthesis, from suppression of normal gland function due to hypercalcemia, or from delayed maturation of parathyroid function. (See What happens in acute hypoparathyroidism.) PTH isn’t regulated by the pituitary or hypothalamus. It normally maintains blood calcium levels by increasing bone resorption and GI absorption of calcium. It also maintains an inverse relationship between serum calcium and phosphate levels by inhibiting phosphate reabsorption in the renal tubules. Abnormal PTH production disrupts this balance. The incidence is 4 out of 100,000 people. Incidence of the idiopathic and reversible forms is highest in children; that of the irreversible acquired form, in older patients who have undergone surgery for hyperthyroidism or other head and neck conditions.
Treatment
Because calcium absorption from the small intestine requires the presence of vitamin D, treatment includes vitamin D and calcium supplements. Therapy is usually lifelong, except for the reversible form of the disease. If the patient can’t tolerate the pure form of vitamin D, alternatives include dihydrotachysterol, if hepatic and renal function is adequate, and calcitriol, if it’s severely compromised. In patients with preexisting hypomagnesemia, this condition must be corrected to treat the resulting hypocalcemia. A high-calcium, low-phosphorous diet is recommended. Acute life-threatening tetany requires immediate I.V. administration of calcium to raise serum calcium levels. The patient who’s awake and able to cooperate can help raise serum calcium levels by breathing into a paper bag and then inhaling his own carbon dioxide; this produces hypoventilation and mild respiratory acidosis. Sedatives and anticonvulsants may control spasms until calcium levels rise. Chronic tetany requires maintenance therapy with oral calcium and vitamin D supplements.