[Hypocalcemic crisis. Hypoparathyroidism--non-parathyroid origin--the most frequent form: hyperventilation syndrome]

Hypocalcemic crisis presents with the classical symptomatology of tetany plus extrapyramidal symptoms and a disordering of consciousness extending even to coma. It develops when the concentration of ionized serum calcium declines rapidly, and is very rarely found in chronic hypocalcemia. In terms of its etiology, various forms of parathyroid deficiency, and nonparathyrogenic diseases associated with hypocalcemia may be involved. Since in the latter the concentration of albumin is also diminished, and thus ionized calcium decreases to only a small extent, hypocalcemic crisis in these conditions is rare. The most common clinical form is normocalcemic tetany that occurs within the framework of the hyperventilation syndrome. Here, the ionized calcium fraction is temporarily reduced by marked alkalosis. Today, laboratory findings render establishment of the diagnosis simple. Acute therapy takes the form of parenteral calcium administration, and for long-term treatment, vitamin D metabolites, possibly in combination with oral calcium replacement is employed.