{"id":4422627,"date":"2025-01-12T08:24:10","date_gmt":"2025-01-12T14:24:10","guid":{"rendered":"https:\/\/myendoconsult.com\/learn\/topics\/storage-diseases\/"},"modified":"2025-01-12T08:27:48","modified_gmt":"2025-01-12T14:27:48","slug":"storage-diseases","status":"publish","type":"oen_topic","link":"https:\/\/myendoconsult.com\/learn\/topics\/storage-diseases\/","title":{"rendered":"Storage Diseases"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">OVERVIEW OF LYSOSOMAL STORAGE DISORDERS<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Lysosomes<\/strong>: Membrane\u2010bound cytoplasmic organelles containing enzymes for degrading sphingolipids, mucopolysaccharides, and glycoproteins.<\/li>\n\n\n\n<li><strong>Enzyme deficiencies<\/strong> \u2192 accumulation of partially degraded substrate \u2192 cell distension \u2192 disruption of cellular function.<\/li>\n\n\n\n<li><strong>Clinical presentation<\/strong> depends on the site(s) and extent of abnormal substrate accumulation.<\/li>\n\n\n\n<li><strong>Categories<\/strong>:\n<ol class=\"wp-block-list\">\n<li><strong>Sphingolipidoses<\/strong> (focus of this summary)<\/li>\n\n\n\n<li>Mucopolysaccharidoses (e.g., Hurler syndrome)<\/li>\n\n\n\n<li>Glycoproteinoses (e.g., sialidosis, mannosidosis)<\/li>\n\n\n\n<li>Mucolipidoses (disorders of lysosomal enzyme transport)<\/li>\n\n\n\n<li>Lysosomal membrane transport disorders (e.g., sialic acid storage disease, cystinosis)<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n\n\n\n<p><strong>Sphingolipidoses<\/strong> include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Tay\u2010Sachs disease<\/li>\n\n\n\n<li>Niemann\u2010Pick disease<\/li>\n\n\n\n<li>Gaucher disease<\/li>\n\n\n\n<li>Metachromatic leukodystrophy<\/li>\n\n\n\n<li>Fabry disease<\/li>\n\n\n\n<li>GM1 gangliosidosis<\/li>\n\n\n\n<li>Krabbe disease<\/li>\n\n\n\n<li>Multiple sulfatase deficiency<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">SPHINGOLIPIDS AND CERAMIDE<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Sphingolipids<\/strong>: Contain sphingosine (18\u2010carbon amino alcohol synthesized from palmitic acid and serine).<\/li>\n\n\n\n<li>A <strong>long\u2010chain fatty acid<\/strong> bound in peptide linkage to sphingosine \u2192 forms <strong>ceramide<\/strong>.<\/li>\n\n\n\n<li>Sphingolipids differ by the polar group linked to the C\u20101 hydroxyl of the ceramide moiety.<\/li>\n\n\n\n<li>Some are concentrated in nervous tissue:\n<ul class=\"wp-block-list\">\n<li>Gangliosides (in ganglion cells)<\/li>\n\n\n\n<li>Cerebrosides and cerebroside sulfatides (in myelin)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Sphingomyelin<\/strong> (the phosphorylcholine ester of ceramide) is found in almost every cell type.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">TAY\u2010SACHS DISEASE<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cause<\/strong>: Deficiency of lysosomal enzyme <strong>\u03b2\u2010hexosaminidase A (Hex A)<\/strong> \u2192 accumulation of gangliosides.<\/li>\n\n\n\n<li><strong>Inheritance<\/strong>: Autosomal recessive; carrier frequency ~1 in 25 among Ashkenazi Jews; disease incidence ~1 in 3600 in this population.<\/li>\n\n\n\n<li><strong>Onset<\/strong>: Usually by 6 months of age; progressive neurologic deficits (e.g., hypotonia, hyperreflexia, weakness, spasticity, seizures, blindness, loss of motor function).<\/li>\n\n\n\n<li><strong>Pathology<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Destructive swelling of ganglion cells<\/li>\n\n\n\n<li>Widespread gliosis \u2192 cranial enlargement<\/li>\n\n\n\n<li>Cherry\u2010red spots on the macula<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Course<\/strong>: Rapidly progressive; typical life expectancy 2\u20105 years.<\/li>\n\n\n\n<li><strong>Testing<\/strong>: DNA mutation analysis; enzyme assays for leukocyte Hex A activity.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">NIEMANN\u2010PICK DISEASE (NPD)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>General<\/strong>: Sphingomyelin\u2010cholesterol lipidosis; rare autosomal recessive disorders; 3 main clinical forms (type A, B, C).<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">NPD Type A and B<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cause<\/strong>: Mutations in the gene encoding <strong>sphingomyelin phosphodiesterase\u20101<\/strong> \u2192 deficiency of <strong>acid sphingomyelinase<\/strong> activity.<\/li>\n\n\n\n<li><strong>Type A<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Complete absence of acid sphingomyelinase<\/li>\n\n\n\n<li>Early onset, hepatosplenomegaly by 3 months<\/li>\n\n\n\n<li>Respiratory failure, neurologic dysfunction<\/li>\n\n\n\n<li>Death by 2\u20133 years of age<\/li>\n\n\n\n<li>Macular cherry\u2010red spots often present by 1 year<\/li>\n\n\n\n<li>Lipid\u2010laden foam cells in tissues<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Type B<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Partial acid sphingomyelinase deficiency (~5% normal)<\/li>\n\n\n\n<li>Later onset than type A<\/li>\n\n\n\n<li>Hepatosplenomegaly, thrombocytopenia in early childhood<\/li>\n\n\n\n<li>Delayed skeletal maturation, <a href=\"https:\/\/myendoconsult.com\/learn\/evaluation-of-short-stature\/\"  data-wpil-monitor-id=\"301\">short stature<\/a>, interstitial lung disease, macular cherry\u2010red spots<\/li>\n\n\n\n<li>Absent or late neurologic involvement<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Diagnosis<\/strong>: Biochemical testing for acid sphingomyelinase; molecular genetic testing.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">NPD Type C<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cause<\/strong>: Mutations in <strong>NPC1 or NPC2<\/strong> genes (key in intracellular cholesterol transport).<\/li>\n\n\n\n<li><strong>Presentation<\/strong>: Any age; cerebellar ataxia, impaired vertical gaze, cognitive issues, dysphagia, hepatosplenomegaly.<\/li>\n\n\n\n<li><strong>Mechanism<\/strong>: Lipid accumulation + neuronal degeneration.<\/li>\n\n\n\n<li><strong>Diagnosis<\/strong>: Biochemical tests on cultured fibroblasts; molecular genetic testing.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">GAUCHER DISEASE (GD)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cause<\/strong>: Deficiency of <strong>glucocerebrosidase<\/strong> (autosomal recessive), due to mutations in the gene encoding this enzyme.<\/li>\n\n\n\n<li><strong>Accumulation<\/strong>: Glucocerebrosides in macrophages \u2192 \u201cGaucher cells\u201d (wrinkled tissue paper appearance).<\/li>\n\n\n\n<li><strong>Prevalence<\/strong>: Most common lysosomal storage disorder (1 in 75,000).<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Clinical Types<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Type 1 (Chronic Adult Form)<\/strong>:\n<ul class=\"wp-block-list\">\n<li>~90% of cases<\/li>\n\n\n\n<li>More frequent in Ashkenazi Jews<\/li>\n\n\n\n<li>Age of onset: 1 year to adulthood<\/li>\n\n\n\n<li>Key features: Massive splenomegaly, hepatomegaly, bone disease (osteoporosis, avascular necrosis, bone pain), thrombocytopenia<\/li>\n\n\n\n<li>Erlenmeyer flask deformity (distal femur)<\/li>\n\n\n\n<li>Pingueculae on the conjunctiva<\/li>\n\n\n\n<li>Neurologic involvement absent<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Type 2 (Acute Neuronopathic)<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Rarest<\/li>\n\n\n\n<li>Fatal by age 2 years<\/li>\n\n\n\n<li>Onset in first year with rapid neurologic deterioration (oculomotor problems, hypertonia, rigidity, seizures)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Type 3 (Chronic Neuronopathic)<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Later onset than type 2<\/li>\n\n\n\n<li>Less severe neurologic involvement than type 2<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Diagnosis<\/strong>: DNA mutation analysis; leukocyte glucocerebrosidase enzyme assay.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">METACHROMATIC LEUKODYSTROPHY (MLD)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cause<\/strong>: Deficiency of <strong>arylsulfatase A<\/strong> (autosomal recessive), leading to defective desulfation of cerebroside sulfate.<\/li>\n\n\n\n<li><strong>Key feature<\/strong>: Sulfate accumulation \u2192 demyelination in CNS + peripheral nerves.<\/li>\n\n\n\n<li><strong>Forms<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Late infantile (onset 6 months\u20132 years): ataxia, hypotonia, regression of motor skills, optic atrophy<\/li>\n\n\n\n<li>Juvenile<\/li>\n\n\n\n<li>Adult<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Visceral involvement<\/strong>: Less prominent than CNS involvement.<\/li>\n\n\n\n<li><strong>Ancillary findings<\/strong>: EMG shows decreased nerve conduction velocity; CSF with high protein.<\/li>\n\n\n\n<li><strong>Diagnosis<\/strong>: Enzyme assay for arylsulfatase A in leukocytes.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">FABRY DISEASE<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cause<\/strong>: Deficiency of <strong>\u03b1\u2010galactosidase A<\/strong> \u2192 accumulation of globotriaosylceramide (Gb3).<\/li>\n\n\n\n<li><strong>Inheritance<\/strong>: X\u2010linked recessive.<\/li>\n\n\n\n<li><strong>Tissue involvement<\/strong>: Vascular endothelium, glomeruli, distal renal tubules.<\/li>\n\n\n\n<li><strong>Clinical<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Typically starts in adolescence or early adulthood.<\/li>\n\n\n\n<li>Neuropathic pain in extremities<\/li>\n\n\n\n<li>Diffuse angiokeratomas (especially in periumbilical\/groin areas)<\/li>\n\n\n\n<li>Corneal opacities (cornea verticillata)<\/li>\n\n\n\n<li>Hypohidrosis\/anhidrosis<\/li>\n\n\n\n<li>Cardiovascular disease (CAD, strokes, peripheral disease)<\/li>\n\n\n\n<li>Renal failure (proteinuria, edema)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Diagnosis<\/strong>: Low leukocyte \u03b1\u2010galactosidase A activity; molecular genetic testing.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>OVERVIEW OF LYSOSOMAL STORAGE DISORDERS Sphingolipidoses include: SPHINGOLIPIDS AND CERAMIDE TAY\u2010SACHS DISEASE NIEMANN\u2010PICK DISEASE (NPD) NPD Type A and B NPD Type C GAUCHER DISEASE (GD) Clinical Types METACHROMATIC LEUKODYSTROPHY (MLD) FABRY DISEASE<\/p>\n","protected":false},"featured_media":0,"template":"","oen_topic_chapter":[689],"class_list":["post-4422627","oen_topic","type-oen_topic","status-publish","hentry","oen_topic_chapter-obesity-medicine","post-wrapper","thrv_wrapper"],"_links":{"self":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422627","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic"}],"about":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/types\/oen_topic"}],"version-history":[{"count":3,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422627\/revisions"}],"predecessor-version":[{"id":4422630,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422627\/revisions\/4422630"}],"wp:attachment":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/media?parent=4422627"}],"wp:term":[{"taxonomy":"oen_topic_chapter","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic_chapter?post=4422627"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}