viagra effect on refractory period D in glycosaminoglycan breakdown. Glycosaminoglycans (previously termed mucopolysaccharides) are polysaccharides abundant on cell surfaces and in extracellular matrix and structures. Enzyme deficiencies that prevent glycosaminoglycan breakdown cause accumulation of glycosaminoglycan fragments in lysosomes and cause extensive bone, soft tissue, and cns changes. Inheritance is usually autosomal recessive (except for mps type ii). Age at presentation, clinical manifestations, and severity vary by type. Common manifestations include coarse facial features, neurodevelopmental delays and regression, joint contractures, organomegaly, stiff hair, progressive respiratory insufficiency (caused by airway obstruction and sleep apnea), cardiac valvular disease, skeletal changes, and cervical vertebral subluxation. viagra for sale buy viagra online viagra online viagra online viagra without a doctor prescription cheap viagra online buy cheap viagra viagra for sale buy viagra Diagnosis is suggested by history, physical examination, bone abnormalities (eg, dysostosis multiplex) found during skeletal survey, and elevated total and fractionated urinary glycosaminoglycans. Diagnosis is confirmed by enzyme analysis of cultured fibroblasts (prenatal) or peripheral wbcs (postnatal). Additional testing is required to monitor organ-specific changes (eg, echocardiography for valvular disease, audiometry for hearing changes). Treatment of mps type i (hurler's disease) is enzyme replacement with î±-l-iduronidase, which effectively halts progression and reverses all non-cns complications of the disease. Hematopoietic stem cell (hsc) transplantation has also shown promise in early studies but is ineffective for cns disease. The combination of enzyme replacement and hsc transplantation is under study. Sphingolipidoses: sphingolipids are normal lipid components of cell membranes; they accumulate in lysosomes and cause extensive neuronal, bone, and other changes when enzyme deficiencies prevent their breakdown. Although incidence is low, carrier rate of some forms is high. Gaucher's disease is the most common sphingolipidosis. Others include niemann-pick, tay-sachs, sandhoff's, fabry's, krabbe's, and cholesteryl ester storage diseases and metachromatic leukodystrophy. Gaucher's disease gaucher's disease is a sphingolipidosis resulting from glucocerebrosidase deficiency, causing deposition of glucocerebroside and related compounds. Symptoms and signs vary by type but are most commonly hepatosplenomegaly o.