hypophosphatasia

An abnormally low content of alkaline phosphatase in the circulating blood. SYN: hypophosphatasemia.

- adult h. an autosomal dominant trait with early loss of teeth, bowing, and beaten-copper skull; there is evidence that the basic defect is in liver alkaline phosphatase.

- childhood h. a relatively mild autosomal recessive form of h.; it may be allelic with congenital h..

- congenital h. [MIM*241500] a rare disorder associated with a low level of serum alkaline phosphatase, hyperphosphaturia, hypercalcemia, skeletal abnormalities, pathologic fractures, craniostenosis, premature loss of teeth, and often early death; eyes may show blue sclerae, lid retraction, band-shaped keratopathy, cataracts, papilledema, and optic atrophy; autosomal recessive inheritance, caused by mutation in the liver alkaline phosphatase gene (ALPL) on chromosome 1p.

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hy·po·phos·pha·ta·sia .hī-pō-.fäs-fə-'tā-zh(ē-)ə n a congenital metabolic disorder characterized by a deficiency of alkaline phosphatase and usu. resulting in demineralization of bone

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hy·po·phos·pha·ta·sia (hi″po-fos″fə-taґzhə) [hypo- + phosphatase + -ia] an inherited metabolic disorder caused by mutation in the ALPL gene (locus: 1p36.1-p34), which encodes alkaline phosphatase; the resulting serum and bone enzyme deficiency leads to hypercalcemia, ethanolamine phosphatemia, and ethanolamine phosphaturia. Clinical manifestations include severe skeletal defects resembling vitamin D–resistant rickets, failure of the calvaria to calcify, dyspnea, cyanosis, vomiting, constipation, renal calcinosis, failure to thrive, movement disorders, beading where the ribs meet their cartilages, and rachitic bone changes (bowleg). There are three clinical types based upon age of onset and severity of symptoms. Two are autosomal recessive: the infantile type is the most severe, lethal in over half the cases; and the childhood type usually has as its first symptom spontaneous loss of deciduous teeth. The adult type is the mildest and is autosomal dominant. See also pseudohypophosphatasia.