Contributor: Gordon K. Klintworth
Glycogenosis type II (glycogen storage disease type II, acid maltase deficiency, cardiomegalia glycogenica diffusa, acid-alpha-glucosidase deficiency, Pompe disease) is one of many types of inherited glycogen storage disease. The severe condition has an autosomal recessive mode of inheritance and a considerable genetic heterogeneity exists. Three types are recognized [glycogen storage disease type II - infantile, glycogen storage disease type II - juvenile, glycogen storage disease type II - adult]. The genetic defect causes a deficiency in the lysosomal enzyme acid alpha-glucosidase and this leads to a massive intralysosomal accumulation of glycogen in nearly all tissues of the body, especially muscle, liver, heart, and brain. In contrast to the normal liver and other cells in which glycogen granules are dispersed throughout the cytoplasm, glycogen is concentrated in abnormally distended lysosomes. Cardiomegaly and profound hypotonia are the earliest signs, appearing at birth or shortly thereafter. The extraocular muscle fibers contain an abundance of free glycogen stored in the lysosomes and strabismus occurs in the infantile form. Suprisingly the eyes are clinically normal despite of widespread accumulation of glycogen in corneal endothelial cells, retinal ganglion cells, Müller cells, smooth and striated ocular muscle fibers, and fibroblasts of the cornea, conjunctiva, sclera, iris, and choroid. One of the few cell types not affected is the retinal pigment epithelium.
not affected is the retinal pigment epithelium.