Lysosomal Substrate Accumulation Module

Metabolism Module lysosomal_substrate_accumulation 60 disorders Pathograph 5

A conserved pathological module representing the shared core of the lysosomal storage diseases (LSDs): an inherited deficiency of a specific lysosomal hydrolase (or of a non-enzymatic protein/transporter essential for normal lysosomal function) blocks catabolism of a macromolecular substrate, which then accumulates undegraded within the lysosome. Progressive intralysosomal storage distends the organelle and impairs lysosome function, triggering a secondary cascade of autophagic-flux block, disturbed signalling, mitochondrial and calcium dysregulation. The affected cell type — often only a subset of cells determined by where the substrate is normally turned over — undergoes storage-cell transformation, cytotoxicity, and (in the CNS) neuroinflammation and neurodegeneration, producing progressive multi-organ disease. This conserved core is shared across sphingolipidoses, mucopolysaccharidoses, glycoproteinoses, glycogenoses (Pompe), and free-substrate transport defects. Individual disorder entries declare conformance via conforms_to on their pathophysiology nodes, substituting the disorder-specific deficient enzyme, stored substrate, and storage cell type while preserving the conserved deficiency -> accumulation -> lysosomal dysfunction -> cytotoxicity -> multisystem disease chain.

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Pathophysiology Nodes

5 shared nodes are defined in this module.

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Cell Types

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Biological Processes

macromolecule catabolic process GO:0009057 ↓ DECREASED autophagy GO:0006914 ↕ DYSREGULATED lysosome organization GO:0007040 ↕ DYSREGULATED apoptotic process GO:0006915 ↑ INCREASED inflammatory response GO:0006954 ↑ INCREASED

Notes

This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "lysosomal_substrate_accumulation# Lysosomal Substrate Accumulation"). The module defines the expected pathophysiology structure; conforming nodes in disorder files should substitute the disorder-specific deficient gene/enzyme and stored substrate while preserving the conserved cascade. Key disorder-specific substitutions: Gaucher uses glucocerebrosidase (GBA1) deficiency and glucocerebroside storage in macrophage-derived Gaucher cells (CL:0000235); Tay-Sachs/Sandhoff use hexosaminidase deficiency and GM2 ganglioside storage in neurons (CL:0000540); Fabry uses alpha-galactosidase A deficiency and Gb3 storage in endothelium, podocytes, and cardiomyocytes; the mucopolysaccharidoses use specific glycosaminoglycan-degrading enzyme deficiencies and GAG storage; Pompe uses acid alpha-glucosidase deficiency and lysosomal glycogen storage in myofibers. Evidence here is drawn from cross-LSD reviews documenting the conserved cascade rather than any single disease; evidence_source is OTHER because these are reviews synthesizing data across multiple study types. The key conformance target is the central effector node "Lysosomal Substrate Accumulation".

Discussions and Knowledge Gaps

Does receptor-mediated CNS delivery of a replacement lysosomal enzyme convert a corrected central storage biomarker into durable neurologic benefit, and at what point in the disease course does that conversion stop being possible?

KNOWLEDGE GAP OPEN gap_cns_delivery_biomarker_versus_clinical_benefit

Attached to: Lysosomal Substrate Accumulation Progressive Multisystem and Neurodegenerative Disease

Conventional intravenous enzyme replacement corrects visceral storage but is excluded from the CNS, which is why the neuronopathic forms of most members of this module have remained untreatable while their visceral disease responds. Brain-penetrant, transferrin-receptor-targeted fusion enzymes break that barrier: in March 2026 tividenofusp alfa became the first such agent approved (US accelerated approval) for the neurologic manifestations of MPS II. The gap is that the approval rests on reduction of CSF heparan sulphate — a storage biomarker sitting at this module's central effector node — and not on a measured neurocognitive outcome, with clinical benefit still to be verified in a confirmatory trial. Curators of conforming disorders must therefore record the biomarker claim and the clinical-benefit claim as separate assertions, and must not curate CSF substrate correction as evidence of neurologic efficacy. The same caution applies to the intrathecal and intracerebroventricular delivery routes and to CNS-directed gene therapy, which are evaluated against the same surrogate.

Do heterozygous loss-of-function carriers of lysosomal storage disease genes other than GBA1 carry an increased risk of adult-onset neurodegeneration, and is partial lysosomal dysfunction sufficient to drive it without detectable substrate storage?

KNOWLEDGE GAP OPEN gap_heterozygous_lsd_carrier_neurodegeneration_risk

Attached to: Autophagic-Lysosomal Dysfunction and Secondary Cascade Storage-Cell Cytotoxicity and Neuroinflammation

This module is written for biallelic disease, where storage is the proximate cause of cytotoxicity. GBA1 established that a single loss-of-function allele — carrier status for a member of this group — is among the strongest genetic risk factors for Parkinson disease, without causing Gaucher disease. Whether that is a GBA1 peculiarity or a general property of partial lysosomal dysfunction is unresolved, and it determines whether carrier status in the other members belongs in their entries at all. Recent MCOLN1 findings extend the question to the mucolipidosis IV gene. Curators should treat a heterozygous-carrier neurodegeneration claim as a separate, weaker assertion than the biallelic storage disease, and should not model it as this module's storage-driven chain: the proposed lesion is reduced lysosomal function without demonstrable substrate accumulation.

Is TFEB activity suppressed or pathologically over-activated in cells that are actively storing lysosomal substrate, and does therapeutic benefit come from raising it or from normalizing it in either direction?

KNOWLEDGE GAP OPEN gap_tfeb_direction_of_dysregulation_in_storage

Attached to: Autophagic-Lysosomal Dysfunction and Secondary Cascade

TFEB is the master transcriptional regulator of lysosomal biogenesis and autophagy, and TFEB activation has been pursued as a substrate-clearing strategy across this disease group on the assumption that storage suppresses it. Work in a Niemann-Pick type C cell model reports the opposite baseline — TFEB already over-activated and nuclear because of chronic lysosomal stress — with levacetylleucine, an approved NPC therapy, acting by reducing nuclear TFEB rather than raising it. If the baseline direction differs by disorder, cell type, or stage, then "TFEB activation" is not a coherent shared therapeutic rationale for this module, and a conforming disorder entry should curate the measured direction in its own cells rather than inheriting a directional assumption. Note the finding is from a HeLa cell model and has not been shown in patient neurons.

Does therapeutic benefit at this node come from activating the endolysosomal two-pore channel TPC2 or from inhibiting it — and is "TPC2 agonism" even one pharmacology, given that the channel's ion selectivity is set by which ligand opens it?

CONTROVERSY OPEN controversy_tpc2_direction_of_modulation

Attached to: Lysosomal Substrate Accumulation Autophagic-Lysosomal Dysfunction and Secondary Cascade

TPC2 is the most developed pharmacological handle on this module's autophagic-lysosomal node, and the published direction of benefit points both ways. Activating it with a small molecule cleared cholesterol, lipofuscin and Gb3 storage in MLIV, NPC1 and Batten patient fibroblasts and iPSC-derived neurons, and rescued rotarod performance, P62 aggregates and cerebellar astrogliosis in the MLIV mouse. Inhibiting it with trans-Ned-19 reduced infarct volume in rats after middle cerebral artery occlusion, on the argument that excitotoxic over-activation of the same channel drives a hyperfunctional autophagy. In LRRK2 Parkinson's models TPC2 is the pathogenic element: human TPC2 expression phenocopied the G2019S mutation in Drosophila, and the authors conclude that both inhibition and select activation are beneficial. Those results are not simply contradictory, and the reconciling fact is a pharmacological one rather than a disease-specific one. TPC2's ion selectivity depends on which agonist opens it: a NAADP-mimetic evokes robust Ca2+ signals and non-selective cation currents, while a PI(3,5)P2-mimetic evokes weaker Ca2+ signals and Na+-selective currents, and the two are coupled to opposing changes in lysosomal pH and exocytosis. So "a TPC2 agonist" names two different interventions. This matters for reading the storage-rescue result correctly: every experiment in it, including the MLIV mouse, used the PI(3,5)P2-mimetic TPC2-A1-P, not the NAADP-mimetic TPC2-A1-N. In the LRRK2 work the beneficial agonist was likewise one biased to reduce Ca2+ permeability. As of this writing no in vivo efficacy result for a TPC2 agonist rests on the Ca2+-permeable NAADP-like mode. Two things this discussion does not claim. It does not claim the rescue is Ca2+-independent — chelating Ca2+ with BAPTA-AM blunted TPC2-A1-P's effect, and that paper describes A1-P as releasing both Ca2+ and Na+, so the distinction is one of degree and kinetics rather than a clean ion swap. And it does not settle the direction for this module: the storage evidence is the only arm with an in vivo disease model, but TPC2-A1-P was undetectable in plasma and brain by 240 minutes and its dose was picked to sit above threshold for barely 20 minutes, so it is a tool compound and not yet a demonstration that sustained TPC2 activation is safe or sufficient. This complements rather than duplicates gap_tfeb_direction_of_dysregulation_in_storage, which asks the same raise-or-normalize question one step downstream at TFEB. Read together they say the direction is unsettled at both the transcription factor and the channel that mobilizes the Ca2+ reaching it — and the channel adds a dimension TFEB does not have, because a biased agonist can move it in two pharmacologically distinct directions rather than just up or down.

Proposed experiments: Head-to-head TPC2-A1-N, TPC2-A1-P and trans-Ned-19 in one storage model

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Used By Disorder Entries

Adult Neuronal Ceroid Lipofuscinosis via Lipopigment Accumulation in Lysosomes → Lysosomal Substrate Accumulation

Alpha-mannosidosis via MAN2B1 lysosomal alpha-mannosidase deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Mannose-rich oligosaccharide lysosomal storage → Lysosomal Substrate Accumulation

Aspartylglucosaminuria via AGA lysosomal enzyme deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Glycoasparagine substrate accumulation → Lysosomal Substrate Accumulation , Neuronal and glial lysosomal storage → Storage-Cell Cytotoxicity and Neuroinflammation

Attenuated Mucopolysaccharidosis Type I via Lysosomal Glycosaminoglycan Accumulation → Lysosomal Substrate Accumulation

Cholesteryl Ester Storage Disease via Lysosomal Acid Lipase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Cholesteryl Ester and Triglyceride Accumulation → Lysosomal Substrate Accumulation

Chronic Neurovisceral Acid Sphingomyelinase Deficiency via Partial Acid Sphingomyelinase Deficiency from SMPD1 Variants → Lysosomal Hydrolase or Cofactor Deficiency , Intermediate Neurovisceral Sphingomyelin Storage → Lysosomal Substrate Accumulation

Combined Saposin Deficiency via Prosaposin Deficiency and Loss of All Saposins → Lysosomal Hydrolase or Cofactor Deficiency , Combined Multi-Sphingolipid Lysosomal Accumulation → Lysosomal Substrate Accumulation

Congenital Sialidosis Type 2 via Severe Neuraminidase-1 Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Sialyloligosaccharide Lysosomal Accumulation → Lysosomal Substrate Accumulation

DNASE2 Deficiency via Biallelic DNASE2 Loss of Function → Lysosomal Hydrolase or Cofactor Deficiency , Undegraded DNA Accumulation in Macrophage Lysosomes → Lysosomal Substrate Accumulation

Dysostosis Multiplex, Ain-Naz Type via Loss of Mannose-6-Phosphate Tagging of Lysosomal Hydrolases → Lysosomal Hydrolase or Cofactor Deficiency , Multisystem Lysosomal Substrate Accumulation → Lysosomal Substrate Accumulation

Fabry disease via Alpha-galactosidase A deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Gb3 and lyso-Gb3 accumulation → Lysosomal Substrate Accumulation

Galactosialidosis via Cathepsin A (PPCA) Deficiency and Secondary Combined NEU1/GLB1 Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Sialyloligosaccharide Lysosomal Accumulation → Lysosomal Substrate Accumulation , Progressive Multisystem and Neurodegenerative Disease

Gaucher Disease via Glucocerebrosidase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Glucocerebroside Accumulation in Macrophages → Lysosomal Substrate Accumulation

Gaucher Disease Due To Saposin C Deficiency via Saposin C Deficiency from PSAP Variants → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Glucosylceramide Accumulation → Lysosomal Substrate Accumulation

Glycoprotein Storage Disease via Lysosomal Glycosidase Deficiency and Impaired Glycoprotein Catabolism → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Oligosaccharide Accumulation → Lysosomal Substrate Accumulation , Neuroinflammation and Neurodegeneration → Storage-Cell Cytotoxicity and Neuroinflammation

GM1 Gangliosidosis Type 1 via GLB1 Loss of Function and Beta-Galactosidase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal GM1 Ganglioside Accumulation in Neurons → Lysosomal Substrate Accumulation , Neuronal Apoptosis → Storage-Cell Cytotoxicity and Neuroinflammation , Progressive Neurodegeneration → Progressive Multisystem and Neurodegenerative Disease , Multisystem Somatic Storage → Progressive Multisystem and Neurodegenerative Disease

GM1 Gangliosidosis Type 2 via Partial Beta-Galactosidase Deficiency and GM1 Ganglioside Accumulation → Lysosomal Hydrolase or Cofactor Deficiency , Neuronal GM1 Storage and Neurodegeneration → Lysosomal Substrate Accumulation

GM1 Gangliosidosis Type 3 via Partial Beta-Galactosidase Deficiency with Basal Ganglia GM1 Accumulation → Lysosomal Substrate Accumulation

GNPTG-Mucolipidosis via GlcNAc-1-Phosphotransferase Gamma-Subunit Deficiency and M6P Targeting Failure → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Substrate Accumulation in Connective Tissue → Lysosomal Substrate Accumulation

Hereditary Spastic Paraplegia 48 via Aberrant Endolysosome Accumulation → Lysosomal Substrate Accumulation

Hunter syndrome via Heparan sulfate and dermatan sulfate lysosomal accumulation → Lysosomal Substrate Accumulation

Hurler syndrome via Dermatan sulfate and heparan sulfate accumulation → Lysosomal Substrate Accumulation

Infantile-Onset Pompe Disease via Lysosomal glycogen accumulation → Lysosomal Substrate Accumulation

Juvenile Neuronal Ceroid Lipofuscinosis via Lysosomal Ceroid-Lipofuscin Storage → Lysosomal Substrate Accumulation

Juvenile Sialidosis Type 2 via Neuraminidase-1 Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Sialyloligosaccharide Lysosomal Accumulation → Lysosomal Substrate Accumulation

Kanzaki Disease via Alpha-N-Acetylgalactosaminidase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Tn-antigen Glycopeptide Accumulation → Lysosomal Substrate Accumulation

Krabbe Disease via GALC Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Psychosine Accumulation → Lysosomal Substrate Accumulation , Proteostasis Failure → Autophagic-Lysosomal Dysfunction and Secondary Cascade

Krabbe Disease Due To Saposin A Deficiency via Saposin A Deficiency from PSAP Variants → Lysosomal Hydrolase or Cofactor Deficiency , Galactosylceramide Accumulation and Demyelination → Lysosomal Substrate Accumulation , Autophagic-Lysosomal Dysfunction → Autophagic-Lysosomal Dysfunction and Secondary Cascade

Late-Onset Pompe Disease via Attenuated Lysosomal Glycogen Accumulation in Skeletal and Respiratory Muscle → Lysosomal Substrate Accumulation , Lysosomal Glycogen Accumulation in Vascular and Visceral Smooth Muscle → Lysosomal Substrate Accumulation

Lysosomal Acid Phosphatase Deficiency via Lysosomal Acid Phosphatase 2 Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Storage in Kidney and CNS → Lysosomal Substrate Accumulation

Maroteaux-Lamy syndrome via ARSB deficiency → Lysosomal Hydrolase or Cofactor Deficiency

Metachromatic Leukodystrophy via Arylsulfatase A Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Saposin B Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Sulfatide Accumulation → Lysosomal Substrate Accumulation

Morquio syndrome via Keratan sulfate-dominant lysosomal storage in cartilage and connective tissue → Lysosomal Substrate Accumulation

Mucolipidosis Type II via GlcNAc-1-Phosphotransferase Deficiency and Mannose-6-Phosphate Targeting Failure → Lysosomal Hydrolase or Cofactor Deficiency , Multisystem Lysosomal Substrate Accumulation → Lysosomal Substrate Accumulation

Mucolipidosis Type III Alpha/Beta via GNPTAB phosphotransferase deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Intracellular glycosphingolipid and glycosaminoglycan storage → Lysosomal Substrate Accumulation

Mucolipidosis Type IV via TRPML1 Channel Dysfunction and Autophagic-Lysosomal Failure → Autophagic-Lysosomal Dysfunction and Secondary Cascade , Lysosomal Storage and Neurodegeneration → Lysosomal Substrate Accumulation

Mucopolysaccharidosis type IX via HYAL1 hyaluronidase deficiency → Lysosomal Hydrolase or Cofactor Deficiency

Mucopolysaccharidosis type X via ARSK glucuronate 2-sulfatase deficiency → Lysosomal Hydrolase or Cofactor Deficiency

Mucopolysaccharidosis-Plus Syndrome via Glycosaminoglycan Accumulation With Normal Lysosomal Hydrolase Activity → Lysosomal Substrate Accumulation , Endolysosomal Compartment Expansion and Over-Acidification → Autophagic-Lysosomal Dysfunction and Secondary Cascade , Renal Podocyte Storage and Glomerular Destruction → Storage-Cell Cytotoxicity and Neuroinflammation , Progressive Multisystem Disease With Plus Features → Progressive Multisystem and Neurodegenerative Disease

NAGA Deficiency Type 3 via Alpha-N-Acetylgalactosaminidase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Glycoconjugate Accumulation → Lysosomal Substrate Accumulation

Neuronal Ceroid Lipofuscinosis via Toxic Endo-Lysosomal Storage → Lysosomal Substrate Accumulation

Neuronal Ceroid Lipofuscinosis 1 via PPT1 lysosomal depalmitoylation failure → Lysosomal Substrate Accumulation

Neuronal Ceroid Lipofuscinosis 2 via TPP1 lysosomal peptidase deficiency → Lysosomal Substrate Accumulation

Neuronal Ceroid Lipofuscinosis 3 via CLN3 endolysosomal membrane dysfunction → Lysosomal Substrate Accumulation

Neuronal Ceroid Lipofuscinosis 7 via Lysosomal autofluorescent storage material accumulation → Lysosomal Substrate Accumulation

Niemann-Pick Disease Type A via SMPD1 Loss of Function and Acid Sphingomyelinase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Sphingomyelin and Secondary Lipid Accumulation → Lysosomal Substrate Accumulation

Niemann-Pick Disease Type B via Residual Acid Sphingomyelinase Activity from SMPD1 Variants → Lysosomal Hydrolase or Cofactor Deficiency , Visceral Sphingomyelin Storage in the Reticuloendothelial System → Lysosomal Substrate Accumulation

Niemann-Pick Disease Type C via Lysosomal Unesterified Cholesterol Accumulation → Lysosomal Substrate Accumulation

Niemann-Pick Disease Type E via Lysosomal Sphingomyelin and Lipid Storage with Foam Cell Infiltration → Lysosomal Substrate Accumulation

Pompe Disease via Lysosomal glycogen accumulation → Lysosomal Substrate Accumulation

Sandhoff Disease via Hexosaminidase A and B deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal GM2 and GA2 accumulation in neural cells → Lysosomal Substrate Accumulation

Sanfilippo syndrome via Lysosomal heparan sulfate accumulation → Lysosomal Substrate Accumulation

Schindler Disease via Alpha-N-Acetylgalactosaminidase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Glycopeptide Accumulation → Lysosomal Substrate Accumulation , Neuroaxonal Dystrophy and Neurodegeneration → Progressive Multisystem and Neurodegenerative Disease

Sialidosis type 1 via Sialylated metabolite lysosomal storage → Lysosomal Substrate Accumulation

Sly syndrome via Beta-glucuronidase deficiency → Lysosomal Hydrolase or Cofactor Deficiency

Spinal Muscular Atrophy-Progressive Myoclonic Epilepsy Syndrome via Acid Ceramidase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Ceramide Accumulation and Motor Neuron Degeneration → Lysosomal Substrate Accumulation

Tay-Sachs Disease via Hexosaminidase A deficiency → Lysosomal Hydrolase or Cofactor Deficiency , GM2 ganglioside accumulation in neurons → Lysosomal Substrate Accumulation

Tay-Sachs Disease AB Variant via GM2 Activator Protein Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Neuronal GM2 Ganglioside Accumulation and Neurodegeneration → Lysosomal Substrate Accumulation

Usher Syndrome Type 4 via Impaired Lysosomal Degradation of 3-O-Sulfated Heparan Sulfate → Lysosomal Substrate Accumulation

Wolman Disease via Lysosomal Acid Lipase Deficiency → Lysosomal Hydrolase or Cofactor Deficiency , Lysosomal Cholesteryl Ester and Triglyceride Storage → Lysosomal Substrate Accumulation

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Pathograph

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Pathophysiology

Lysosomal Hydrolase or Cofactor Deficiency

trigger

A monogenic loss-of-function defect reduces the activity of a specific acid hydrolase that degrades a macromolecular substrate within the lysosome, or of a non-enzymatic protein (activator, membrane transporter, or trafficking factor) required for normal lysosomal catabolism. The identity of the deficient enzyme/protein varies by disorder, but the consequence — loss of the catabolic step for a particular substrate — is the conserved trigger of the module.

macromolecule catabolic process GO:0009057 ↓ DECREASED

Used by disorders

Alpha-mannosidosis as MAN2B1 lysosomal alpha-mannosidase deficiency

Aspartylglucosaminuria as AGA lysosomal enzyme deficiency

Cholesteryl Ester Storage Disease as Lysosomal Acid Lipase Deficiency

Chronic Neurovisceral Acid Sphingomyelinase Deficiency as Partial Acid Sphingomyelinase Deficiency from SMPD1 Variants

Combined Saposin Deficiency as Prosaposin Deficiency and Loss of All Saposins

Congenital Sialidosis Type 2 as Severe Neuraminidase-1 Deficiency

DNASE2 Deficiency as Biallelic DNASE2 Loss of Function

Dysostosis Multiplex, Ain-Naz Type as Loss of Mannose-6-Phosphate Tagging of Lysosomal Hydrolases

Fabry disease as Alpha-galactosidase A deficiency

Galactosialidosis as Cathepsin A (PPCA) Deficiency and Secondary Combined NEU1/GLB1 Deficiency

Gaucher Disease as Glucocerebrosidase Deficiency

Gaucher Disease Due To Saposin C Deficiency as Saposin C Deficiency from PSAP Variants

Glycoprotein Storage Disease as Lysosomal Glycosidase Deficiency and Impaired Glycoprotein Catabolism

GM1 Gangliosidosis Type 1 as GLB1 Loss of Function and Beta-Galactosidase Deficiency

GM1 Gangliosidosis Type 2 as Partial Beta-Galactosidase Deficiency and GM1 Ganglioside Accumulation

GNPTG-Mucolipidosis as GlcNAc-1-Phosphotransferase Gamma-Subunit Deficiency and M6P Targeting Failure

Juvenile Sialidosis Type 2 as Neuraminidase-1 Deficiency

Kanzaki Disease as Alpha-N-Acetylgalactosaminidase Deficiency

Krabbe Disease as GALC Deficiency

Krabbe Disease Due To Saposin A Deficiency as Saposin A Deficiency from PSAP Variants

Lysosomal Acid Phosphatase Deficiency as Lysosomal Acid Phosphatase 2 Deficiency

Maroteaux-Lamy syndrome as ARSB deficiency

Metachromatic Leukodystrophy as Arylsulfatase A Deficiency

Metachromatic Leukodystrophy as Saposin B Deficiency

Mucolipidosis Type II as GlcNAc-1-Phosphotransferase Deficiency and Mannose-6-Phosphate Targeting Failure

Mucolipidosis Type III Alpha/Beta as GNPTAB phosphotransferase deficiency

Mucopolysaccharidosis type IX as HYAL1 hyaluronidase deficiency

Mucopolysaccharidosis type X as ARSK glucuronate 2-sulfatase deficiency

NAGA Deficiency Type 3 as Alpha-N-Acetylgalactosaminidase Deficiency

Niemann-Pick Disease Type A as SMPD1 Loss of Function and Acid Sphingomyelinase Deficiency

Niemann-Pick Disease Type B as Residual Acid Sphingomyelinase Activity from SMPD1 Variants

Sandhoff Disease as Hexosaminidase A and B deficiency

Schindler Disease as Alpha-N-Acetylgalactosaminidase Deficiency

Sly syndrome as Beta-glucuronidase deficiency

Spinal Muscular Atrophy-Progressive Myoclonic Epilepsy Syndrome as Acid Ceramidase Deficiency

Tay-Sachs Disease as Hexosaminidase A deficiency

Tay-Sachs Disease AB Variant as GM2 Activator Protein Deficiency

Wolman Disease as Lysosomal Acid Lipase Deficiency

Downstream

Lysosomal Substrate Accumulation Loss of the catabolic step leaves the substrate undegraded, so it accumulates within the lysosome.

Show evidence (1 reference)

PMID:36285443 SUPPORT Other

"They are caused by a deficiency in specific lysosomal hydrolases involved in cellular catabolism, or non-enzymatic proteins essential for normal lysosomal functions."

Establishes the conserved trigger of the module: deficiency of a specific lysosomal hydrolase or of a non-enzymatic protein required for lysosomal function. Evidence source is OTHER because this is a review synthesizing data across many lysosomal storage diseases.

Lysosomal Substrate Accumulation

central effector

The substrate that can no longer be degraded accumulates undegraded within the lysosomal lumen. Storage is frequently restricted to the cell types in which that substrate is normally turned over in greatest quantity (e.g., macrophages for glucocerebroside, neurons for gangliosides), which patterns the organ-specific clinical picture. This intralysosomal accumulation is the central, defining effector event of every lysosomal storage disease and the key conformance target for disorder entries.

Used by disorders

Adult Neuronal Ceroid Lipofuscinosis as Lipopigment Accumulation in Lysosomes

Alpha-mannosidosis as Mannose-rich oligosaccharide lysosomal storage

Aspartylglucosaminuria as Glycoasparagine substrate accumulation

Attenuated Mucopolysaccharidosis Type I as Lysosomal Glycosaminoglycan Accumulation

Cholesteryl Ester Storage Disease as Lysosomal Cholesteryl Ester and Triglyceride Accumulation

Chronic Neurovisceral Acid Sphingomyelinase Deficiency as Intermediate Neurovisceral Sphingomyelin Storage

Combined Saposin Deficiency as Combined Multi-Sphingolipid Lysosomal Accumulation

Congenital Sialidosis Type 2 as Sialyloligosaccharide Lysosomal Accumulation

DNASE2 Deficiency as Undegraded DNA Accumulation in Macrophage Lysosomes

Dysostosis Multiplex, Ain-Naz Type as Multisystem Lysosomal Substrate Accumulation

Fabry disease as Lysosomal Gb3 and lyso-Gb3 accumulation

Galactosialidosis as Sialyloligosaccharide Lysosomal Accumulation

Gaucher Disease as Glucocerebroside Accumulation in Macrophages

Gaucher Disease Due To Saposin C Deficiency as Lysosomal Glucosylceramide Accumulation

Glycoprotein Storage Disease as Lysosomal Oligosaccharide Accumulation

GM1 Gangliosidosis Type 1 as Lysosomal GM1 Ganglioside Accumulation in Neurons

GM1 Gangliosidosis Type 2 as Neuronal GM1 Storage and Neurodegeneration

GM1 Gangliosidosis Type 3 as Partial Beta-Galactosidase Deficiency with Basal Ganglia GM1 Accumulation

GNPTG-Mucolipidosis as Lysosomal Substrate Accumulation in Connective Tissue

Hereditary Spastic Paraplegia 48 as Aberrant Endolysosome Accumulation

Hunter syndrome as Heparan sulfate and dermatan sulfate lysosomal accumulation

Hurler syndrome as Dermatan sulfate and heparan sulfate accumulation

Infantile-Onset Pompe Disease as Lysosomal glycogen accumulation

Juvenile Neuronal Ceroid Lipofuscinosis as Lysosomal Ceroid-Lipofuscin Storage

Juvenile Sialidosis Type 2 as Sialyloligosaccharide Lysosomal Accumulation

Kanzaki Disease as Lysosomal Tn-antigen Glycopeptide Accumulation

Krabbe Disease as Psychosine Accumulation

Krabbe Disease Due To Saposin A Deficiency as Galactosylceramide Accumulation and Demyelination

Late-Onset Pompe Disease as Attenuated Lysosomal Glycogen Accumulation in Skeletal and Respiratory Muscle

Late-Onset Pompe Disease as Lysosomal Glycogen Accumulation in Vascular and Visceral Smooth Muscle

Lysosomal Acid Phosphatase Deficiency as Lysosomal Storage in Kidney and CNS

Metachromatic Leukodystrophy as Sulfatide Accumulation

Morquio syndrome as Keratan sulfate-dominant lysosomal storage in cartilage and connective tissue

Mucolipidosis Type II as Multisystem Lysosomal Substrate Accumulation

Mucolipidosis Type III Alpha/Beta as Intracellular glycosphingolipid and glycosaminoglycan storage

Mucolipidosis Type IV as Lysosomal Storage and Neurodegeneration

Mucopolysaccharidosis-Plus Syndrome as Glycosaminoglycan Accumulation With Normal Lysosomal Hydrolase Activity

NAGA Deficiency Type 3 as Lysosomal Glycoconjugate Accumulation

Neuronal Ceroid Lipofuscinosis as Toxic Endo-Lysosomal Storage

Neuronal Ceroid Lipofuscinosis 1 as PPT1 lysosomal depalmitoylation failure

Neuronal Ceroid Lipofuscinosis 2 as TPP1 lysosomal peptidase deficiency

Neuronal Ceroid Lipofuscinosis 3 as CLN3 endolysosomal membrane dysfunction

Neuronal Ceroid Lipofuscinosis 7 as Lysosomal autofluorescent storage material accumulation

Niemann-Pick Disease Type A as Lysosomal Sphingomyelin and Secondary Lipid Accumulation

Niemann-Pick Disease Type B as Visceral Sphingomyelin Storage in the Reticuloendothelial System

Niemann-Pick Disease Type C as Lysosomal Unesterified Cholesterol Accumulation

Niemann-Pick Disease Type E as Lysosomal Sphingomyelin and Lipid Storage with Foam Cell Infiltration

Pompe Disease as Lysosomal glycogen accumulation

Sandhoff Disease as Lysosomal GM2 and GA2 accumulation in neural cells

Sanfilippo syndrome as Lysosomal heparan sulfate accumulation

Schindler Disease as Lysosomal Glycopeptide Accumulation

Sialidosis type 1 as Sialylated metabolite lysosomal storage

Spinal Muscular Atrophy-Progressive Myoclonic Epilepsy Syndrome as Ceramide Accumulation and Motor Neuron Degeneration

Tay-Sachs Disease as GM2 ganglioside accumulation in neurons

Tay-Sachs Disease AB Variant as Neuronal GM2 Ganglioside Accumulation and Neurodegeneration

Usher Syndrome Type 4 as Impaired Lysosomal Degradation of 3-O-Sulfated Heparan Sulfate

Wolman Disease as Lysosomal Cholesteryl Ester and Triglyceride Storage

Downstream

Autophagic-Lysosomal Dysfunction and Secondary Cascade Progressive storage distends the lysosome and impairs its function, initiating a secondary cellular cascade.

Show evidence (2 references)

PMID:36285443 SUPPORT Other

"Lysosomal storage diseases (LSDs) comprise a group of inherited monogenic disorders characterized by lysosomal dysfunctions due to undegraded substrate accumulation."

Defines undegraded substrate accumulation as the characterizing event of the lysosomal storage diseases, the central effector of this module. Evidence source is OTHER because this is a cross-LSD review.

PMID:30651381 SUPPORT Other

"Lysosomal storage diseases (LSDs) are characterized by disturbances in this network and by intralysosomal accumulation of substrates, often only in certain cell types."

Confirms intralysosomal substrate accumulation as the defining feature and documents the conserved cell-type restriction of storage, which underlies the organ-specific substitutions made by conforming disorder nodes. Evidence source is OTHER because this is a review.

Autophagic-Lysosomal Dysfunction and Secondary Cascade

amplifier

Progressive lysosomal storage impairs core lysosome functions, blocking autophagic flux and disturbing membrane repair, exocytosis, lipid homeostasis, and signalling. Substrate accumulation is only the first event of a cascade that includes accumulation of secondary metabolites and impairment of cellular trafficking, cell signalling, mitochondrial function, and calcium homeostasis. This amplifying step converts a single catabolic block into broad cellular dysfunction.

autophagy GO:0006914 ↕ DYSREGULATED lysosome organization GO:0007040 ↕ DYSREGULATED

Used by disorders

Krabbe Disease as Proteostasis Failure

Krabbe Disease Due To Saposin A Deficiency as Autophagic-Lysosomal Dysfunction

Mucolipidosis Type IV as TRPML1 Channel Dysfunction and Autophagic-Lysosomal Failure

Mucopolysaccharidosis-Plus Syndrome as Endolysosomal Compartment Expansion and Over-Acidification

Downstream

Storage-Cell Cytotoxicity and Neuroinflammation Sustained lysosomal and autophagic dysfunction drives storage-cell transformation, cytotoxicity, and, in the CNS, neuroinflammation.

Show evidence (2 references)

PMID:36285443 SUPPORT Other

"A substantial number of studies on the pathogenesis of LSDs has highlighted how the accumulation of lysosomal substrates is only the first event of a cascade of processes including the accumulation of secondary metabolites and the impairment of cellular trafficking, cell signalling, autophagic..."

Documents the conserved secondary cascade (impaired autophagic flux, trafficking, signalling, mitochondrial and calcium homeostasis) that amplifies primary substrate storage into broad cellular dysfunction. Evidence source is OTHER because this is a cross-LSD review.

PMID:30651381 SUPPORT Other

"This Review aims to discuss how lysosomal storage affects functions linked to lysosomes, such as membrane repair, autophagy, exocytosis, lipid homeostasis, signalling cascades and cell viability."

Enumerates the lysosome-linked functions (autophagy, membrane repair, exocytosis, lipid homeostasis, signalling, cell viability) disrupted by storage, supporting this amplifier node. Evidence source is OTHER because this is a review.

Storage-Cell Cytotoxicity and Neuroinflammation

effector

The affected cell becomes an engorged storage cell whose impaired autophagy and lysosomal dysfunction compromise viability, driving apoptotic death. In the central nervous system, impaired neuronal autophagy initiates neuronal damage and activates microglia and astrocytes, producing a neuroinflammatory response that amplifies neurodegeneration. The specific storage cell varies by disorder (lipid-laden macrophage, ganglioside-laden neuron, GAG-laden mesenchymal and neural cells), but the progression from storage to cytotoxicity and inflammation is conserved.

macrophage CL:0000235 neuron CL:0000540

apoptotic process GO:0006915 ↑ INCREASED inflammatory response GO:0006954 ↑ INCREASED

Used by disorders

Aspartylglucosaminuria as Neuronal and glial lysosomal storage

Glycoprotein Storage Disease as Neuroinflammation and Neurodegeneration

GM1 Gangliosidosis Type 1 as Neuronal Apoptosis

Mucopolysaccharidosis-Plus Syndrome as Renal Podocyte Storage and Glomerular Destruction

Downstream

Progressive Multisystem and Neurodegenerative Disease Accumulated cytotoxicity across affected cell types produces progressive organ and nervous-system disease.

Show evidence (2 references)

PMID:30451936 SUPPORT Other

"The pathophysiological mechanism of these diseases has been investigated, indicating impaired autophagy in neuronal damage initiation, association of activated microglia and astrocytes with the neuroinflammatory processes, and involvement of tauopathy."

Establishes the conserved neuronopathic effector mechanism: impaired autophagy initiating neuronal damage and microglial/astrocyte activation driving neuroinflammation. Evidence source is OTHER because this is a review of the mucopolysaccharidoses synthesizing multiple study types.

PMID:30651381 SUPPORT Other

"This Review aims to discuss how lysosomal storage affects functions linked to lysosomes, such as membrane repair, autophagy, exocytosis, lipid homeostasis, signalling cascades and cell viability."

Supports the link from lysosomal storage to compromised cell viability; partial because the quote names cell viability as an affected function without detailing the apoptotic and neuroinflammatory effectors.

Progressive Multisystem and Neurodegenerative Disease

consequence

The lack of degradation and lysosomal storage perturbs cellular homeostasis and, in turn, damages multiple organ systems. The specific clinical pattern (hepatosplenomegaly, skeletal dysplasia, cardiomyopathy, renal disease, psychomotor regression) depends on which cell types store substrate, but the final common outcome of progressive, multisystem, often neurodegenerative disease is conserved across the lysosomal storage diseases.

Used by disorders

Galactosialidosis

GM1 Gangliosidosis Type 1 as Multisystem Somatic Storage

GM1 Gangliosidosis Type 1 as Progressive Neurodegeneration

Mucopolysaccharidosis-Plus Syndrome as Progressive Multisystem Disease With Plus Features

Schindler Disease as Neuroaxonal Dystrophy and Neurodegeneration

Show evidence (1 reference)

PMID:36285443 SUPPORT Other

"In LSDs, the lack of degradation of the accumulated substrate and its lysosomal storage impairs lysosome functions resulting in the perturbation of cellular homeostasis and, in turn, the damage of multiple organ systems."

Directly states the conserved terminal consequence: impaired lysosome function from storage perturbs cellular homeostasis and damages multiple organ systems. Evidence source is OTHER because this is a cross-LSD review.