Tetany is a symptom complex characterized by painful and prolonged contractions of the (generally smooth) muscles. These often appear as convulsions and are usually triggered by hypocalcemia. Adult varieties of the condition that result from calcium or magnesium deficiencies include maternal tetany, parathyroid tetany, osteomalacic tetany, and magnesium tetany. Alkalosis can also produce tetany. Examples include gastric tetany and hyperventilation tetany, following a lengthy period of forced inspiration and expiration. Another form of the disease – grass tetany caused by magnesium deficiency – is found in cattle. Despite these many forms, however, the disease occurs chiefly in infants (neonatal tetany) and young children (infantile tetany) in whom it is normally associated with rickets. It affects males far more than females and, in the absence of proper treatment, frequently proves deadly.

Distribution and Incidence

Because tetany has so often been confused with tetanus, very few data are available on the geographic distribution of the disease. It probably occurs worldwide in the temperate zones, with the highest frequency of neonatal tetany among bottle-fed, black, and prematurely born infants. An abundance of year-round sunshine and, hence, vitamin D may have the effect of reducing the incidence of infantile tetany in the tropics. The incidence of neonatal tetany recorded at New York Hospital between 1940 and 1958 was between 1 per 500 and 1 per 700 births.