What are the sphingolipidoses?

Sphingolipidoses are inherited lysosomal storage diseases in which one enzyme that breaks down a sphingolipid is missing, so that lipid builds up in lysosomes. The main ones are Tay-Sachs and Sandhoff disease (GM2 ganglioside), GM1 gangliosidosis, Gaucher disease (glucocerebroside), Niemann-Pick disease types A and B (sphingomyelin), Fabry disease (globotriaosylceramide), Krabbe disease (galactocerebroside and psychosine), metachromatic leukodystrophy (sulfatides) and Farber disease (ceramide). All are autosomal recessive except Fabry disease, which is X-linked.

Which sphingolipidosis is X-linked?

Fabry disease, caused by variants in the GLA gene that reduce alpha-galactosidase A activity, is the X-linked sphingolipidosis; the others are autosomal recessive. Globotriaosylceramide (Gb3) builds up in blood vessel, kidney, heart and nerve cells, causing burning pain in the hands and feet, angiokeratomas, reduced sweating and corneal opacities in childhood, then kidney failure, heart disease and stroke. Heterozygous women range from no symptoms to severe disease because of X-inactivation.

Which lysosomal storage diseases cause a cherry-red spot?

The classic sphingolipidoses with a cherry-red macula are Tay-Sachs disease, Sandhoff disease, GM1 gangliosidosis and Niemann-Pick disease type A; Farber disease can also cause one, and up to a third of people with Niemann-Pick type B have a cherry-red spot or macular halo. To separate the two exam favorites, check the abdomen: Tay-Sachs has no enlarged liver or spleen, while Niemann-Pick type A has hepatosplenomegaly from early infancy plus lung disease.

How do you tell Tay-Sachs disease from Niemann-Pick disease?

Both can present in infancy with regression and a cherry-red spot. Tay-Sachs is hexosaminidase A deficiency with GM2 ganglioside storage in neurons; it causes an exaggerated startle to noise, seizures and vision loss but no enlargement of the liver or spleen. Niemann-Pick type A is acid sphingomyelinase deficiency with sphingomyelin storage; it causes hepatosplenomegaly by about 3 months, interstitial lung disease and lipid-laden foam cells. Both are autosomal recessive and more common in Ashkenazi Jewish people.

What is the difference between Krabbe disease and metachromatic leukodystrophy?

Both are autosomal recessive leukodystrophies that destroy myelin. Krabbe disease is galactocerebrosidase deficiency: galactocerebroside and toxic psychosine build up, multinucleated globoid cells form, and infants present before age 1 with irritability, stiffness, unexplained fevers and regression. Metachromatic leukodystrophy is arylsulfatase A deficiency with sulfatide buildup, causing central and peripheral demyelination that starts in the second year of life (late infantile), in childhood (juvenile) or in adulthood with psychiatric symptoms.

Which sphingolipidoses can be treated?

In the US, type 1 Gaucher disease is treated with enzyme replacement (imiglucerase, velaglucerase alfa or taliglucerase alfa) or oral substrate reduction (eliglustat or miglustat). Olipudase alfa treats the non-brain manifestations of acid sphingomyelinase deficiency (Niemann-Pick A/B). Fabry disease has enzyme replacement (agalsidase beta, pegunigalsidase alfa) and the oral chaperone migalastat. Early metachromatic leukodystrophy can be treated with the gene therapy atidarsagene autotemcel, and stem cell transplant done early in the disease helps infantile Krabbe disease. Tay-Sachs, Sandhoff, GM1 gangliosidosis and Farber disease get supportive care.

Sphingolipidoses Table: Enzymes, Substrates, Signs & Therapy

Sphingolipids are membrane lipids built on ceramide (sphingosine plus a fatty acid). Lysosomes take them apart one head-group step at a time back to ceramide, and a missing enzyme at any step causes a sphingolipidosis: Tay-Sachs and Sandhoff (GM2 ganglioside), GM1 gangliosidosis, Gaucher (glucocerebroside), Niemann-Pick A/B (sphingomyelin), Fabry (globotriaosylceramide), Krabbe (galactocerebroside and psychosine), metachromatic leukodystrophy (sulfatides) and Farber (ceramide). All are autosomal recessive except Fabry, which is X-linked. On exams, a cherry-red spot points to Tay-Sachs, Sandhoff, GM1 or Niemann-Pick A; hepatosplenomegaly separates Niemann-Pick A from Tay-Sachs; demyelination means Krabbe or MLD. In the US, disease-specific therapy now exists for Gaucher and Niemann-Pick A/B (non-brain disease only), Fabry and early MLD, and stem cell transplant done early in the disease helps infantile Krabbe.

Sphingolipidoses table: enzyme, lipid, inheritance, signs, therapy

Disease	Enzyme (gene)	Stored lipid	Inheritance	Classic signs	US therapy (Oct 2026)
Tay-Sachs	Hexosaminidase A (HEXA)	GM2 ganglioside	AR; about 1 in 27 Ashkenazi Jewish adults are carriers	Normal until 3-6 months, then exaggerated startle to noise, regression, seizures, vision and hearing loss, cherry-red spot; no visceral involvement; death in early childhood	Supportive only
Sandhoff	Hexosaminidase A and B (HEXB)	GM2 ganglioside	AR; no ethnic association	Tay-Sachs picture plus visceral involvement (hepatomegaly, bone changes)	Supportive only
GM1 gangliosidosis (type I)	β-galactosidase (GLB1)	GM1 ganglioside	AR	Infant with coarse facial features, enlarged gums, hepatosplenomegaly, skeletal changes, cherry-red spot and regression	Supportive only
Gaucher	Glucocerebrosidase (GBA1)	Glucocerebroside (glucosylceramide)	AR; common in Ashkenazi Jewish people	Type 1 (about 90%, no primary brain disease): splenomegaly, hepatomegaly, cytopenias (bruising), bone pain crises, osteonecrosis, Erlenmeyer flask femurs, macrophages with a wrinkled tissue-paper look. Type 2: fatal infantile brain disease. Type 3: slower brain disease with supranuclear gaze palsy	ERT (imiglucerase, velaglucerase alfa, taliglucerase alfa) or oral substrate reduction (eliglustat; miglustat when ERT is not an option); none treats brain disease
Niemann-Pick A/B (acid sphingomyelinase deficiency)	Acid sphingomyelinase (SMPD1)	Sphingomyelin	AR; types A and B together about 1 in 250,000; type A about 1 in 40,000 in Ashkenazi Jewish people	Type A: hepatosplenomegaly by 3 months, cherry-red spot, interstitial lung disease, rapid neurodegeneration, death usually by age 3. Type B: organomegaly and lung disease without brain involvement; survival into adulthood. Lipid-laden foam cells	Olipudase alfa (Xenpozyme; US 2022) for non-CNS disease
Fabry	α-galactosidase A (GLA)	Globotriaosylceramide (Gb3; ceramide trihexoside)	X-linked; heterozygous females range from no symptoms to severe disease	Childhood burning pain in hands and feet, angiokeratomas between umbilicus and knees, reduced sweating, corneal opacities (cornea verticillata); later proteinuria and kidney failure, LVH and arrhythmias, stroke	ERT (agalsidase beta, pegunigalsidase alfa) or the oral chaperone migalastat for amenable variants
Krabbe	Galactocerebrosidase (GALC)	Galactocerebroside + psychosine (toxic to myelin-forming cells)	AR	Infant before age 1: irritability, stiffness, feeding problems, fevers without infection, regression, seizures, vision and hearing loss; multinucleated globoid cells; rarely survives past 2	Stem cell transplant early in the disease (prolongs life and improves function in the infantile and late-infantile forms); infantile Krabbe is on the US newborn screening panel
Metachromatic leukodystrophy	Arylsulfatase A (ARSA; rarely saposin B, PSAP)	Sulfatides	AR	Central and peripheral demyelination. Late infantile (second year): loses speech, weakness, walking problems. Juvenile (age 4 to teens): behavior and school decline. Adult: psychiatric symptoms, substance use	Gene therapy, atidarsagene autotemcel (Lenmeldy; US 2024), for presymptomatic late-infantile, presymptomatic early-juvenile and early-symptomatic early-juvenile MLD; allogeneic stem cell transplant for presymptomatic or early-symptomatic juvenile and adult MLD (not late-infantile MLD)
Farber	Acid ceramidase (ASAH1)	Ceramide	AR	Infancy: hoarse voice or weak cry, lumps under the skin (lipogranulomas), swollen painful joints; cherry-red spot	Supportive

Niemann-Pick type C is a different disease: NPC1 or NPC2 variants impair lipid transport, so cholesterol and other lipids pile up; it shows up in childhood with ataxia and vertical supranuclear gaze palsy, not as sphingomyelinase deficiency.

Sphingolipid metabolism in 60 seconds: ceramide is the hub

Every sphingolipid is ceramide plus something:

Cerebrosides = ceramide + one sugar: glucocerebroside (glucose) or galactocerebroside (galactose). Galactocerebroside keeps myelin stable.
Sulfatides = sulfated galactocerebroside, abundant in white matter.
Globosides such as Gb3 = ceramide + three sugars.
Gangliosides = sugar chains carrying sialic acid (1 to 5 residues) on ceramide, concentrated in the brain. In GM1, GM2 and GM3, M means one sialic acid and the number reflects migration order on chromatography.
Sphingomyelin is cleaved straight back to ceramide by acid sphingomyelinase.
Psychosine is galactocerebroside without its fatty acid; it is toxic and drives the demyelination of Krabbe.

Glucocerebroside is the starting point for lactosylceramide, the branch point for gangliosides and globosides, so degradation runs in reverse and funnels back through it:

Lysosomal step	Enzyme	Disease if it's missing
GM1 → GM2 (removes terminal galactose)	GM1 β-galactosidase	GM1 gangliosidosis
GM2 → GM3 (removes N-acetylgalactosamine)	Hexosaminidase A (α + β subunits)	Tay-Sachs (α subunit); Sandhoff (β subunit, so A and B both fail)
Gb3 → lactosylceramide (removes terminal galactose)	α-galactosidase A	Fabry
Sulfatide → galactocerebroside	Arylsulfatase A	MLD
Galactocerebroside → ceramide (also clears psychosine)	Galactocerebrosidase	Krabbe
Glucocerebroside → ceramide + glucose	Glucocerebrosidase	Gaucher
Sphingomyelin → ceramide	Acid sphingomyelinase	Niemann-Pick A/B
Ceramide → sphingosine + fatty acid	Acid ceramidase	Farber

GM3 is trimmed to lactosylceramide by a sialidase, and lactosylceramide is broken down to glucocerebroside before the final step to ceramide. Draw this once and you can rebuild the whole table from it.

How USMLE sorts them

Clue in the stem	Think
Cherry-red spot, regression, no organomegaly	Tay-Sachs
Cherry-red spot plus hepatosplenomegaly and lung disease	Niemann-Pick A
Cherry-red spot plus coarse face and skeletal changes	GM1 gangliosidosis
Exaggerated startle to noise	Tay-Sachs or Sandhoff
Splenomegaly, low platelets, bone crises, Erlenmeyer flask femur	Gaucher type 1
Irritable, stiff infant with unexplained fevers; globoid cells	Krabbe
Gait decline and neuropathy in a toddler, school decline, or psychiatric illness with white-matter disease in an adult	MLD
Burning pain in hands and feet, angiokeratomas, proteinuria, LVH; affected maternal relatives	Fabry
Hoarse cry, swollen joints, nodules under the skin	Farber

Traps:

Fabry is the only X-linked sphingolipidosis, but heterozygous women can be severely affected (X-inactivation). In women, enzyme activity is unreliable, so the diagnosis rests on finding a GLA variant. More X-linked patterns are in the Hurler vs Hunter page, where Hunter is the X-linked mucopolysaccharidosis.
Sandhoff = Tay-Sachs + viscera. The β subunit is part of hexosaminidase A and B, so HEXB variants knock out both enzymes.
Cherry-red spot is not specific to Tay-Sachs. Ask about the liver and spleen.
Gaucher carriers matter: people with one GBA1 variant (and people with Gaucher disease) have a higher risk of Parkinson disease.
MLD pseudodeficiency: some ARSA variants, carried by up to 5-10% of Europeans and North Americans, give very low arylsulfatase A activity without disease, so low enzyme activity alone does not prove MLD.
Ashkenazi Jewish ancestry raises the odds of Tay-Sachs, Gaucher and Niemann-Pick type A, not Sandhoff.

Diagnosis and treatment

Diagnosis: enzyme activity in white blood cells or cultured skin fibroblasts, plus DNA analysis; for Niemann-Pick, prenatal testing by chorionic villus sampling or amniocentesis is possible. Infantile Krabbe is a core condition on the US Recommended Uniform Screening Panel, which lists it as low galactocerebrosidase (GALC) activity with psychosine of 10 nM or more.
Enzyme replacement works on the body, not the brain. Imiglucerase is labeled for non-CNS disease in Gaucher types 1 and 3, and olipudase alfa for non-CNS disease in acid sphingomyelinase deficiency; neither changes neurologic decline.
Substrate reduction (eliglustat, miglustat) blocks glucosylceramide synthase so less glucocerebroside is made. Eliglustat is for adults with type 1 Gaucher who are CYP2D6 extensive, intermediate or poor metabolizers on an FDA-cleared test.
Fabry: agalsidase beta is given IV every 2 weeks from age 2; pegunigalsidase alfa is approved for adults; migalastat is an oral chaperone for adults with an amenable GLA variant (accelerated approval). Supportive care adds pain control (gabapentin, carbamazepine), ACE inhibitors or ARBs for proteinuria, and dialysis or kidney transplant.
MLD gene therapy uses the child's own blood stem cells, given a working ARSA gene by a lentiviral vector. Allogeneic stem cell transplant is not recommended for late-infantile MLD, even before symptoms, and is not offered once neurologic involvement is significant.

Practice question

A 10-month-old boy is evaluated for poor feeding and loss of milestones; he sat unsupported at 6 months but no longer can. His parents are of Ashkenazi Jewish descent, and his abdomen has looked swollen since he was 3 months old. Examination shows hypotonia and massive hepatosplenomegaly, and funduscopy shows a cherry-red spot at each macula. Chest x-ray shows diffuse interstitial infiltrates. Accumulation of which substance best explains these findings?

A. Glucocerebroside B. GM2 ganglioside C. Sphingomyelin D. Galactocerebroside E. Sulfatide

Answer: C. Hepatosplenomegaly from about 3 months, a cherry-red spot, interstitial lung disease and rapid regression are Niemann-Pick type A (infantile acid sphingomyelinase deficiency), which is more common in Ashkenazi Jewish families. Without acid sphingomyelinase, sphingomyelin is not cleaved to ceramide.

A: Gaucher disease also enlarges the liver and spleen, and type 2 adds infantile brain disease, but a cherry-red spot is not a typical Gaucher finding; its classic clues are cytopenias, bone crises and wrinkled tissue-paper macrophages.
B: GM2 ganglioside fits the cherry-red spot and regression of Tay-Sachs, but Tay-Sachs spares the viscera. Sandhoff (also GM2) can enlarge the liver, but it has no Ashkenazi association, and massive early hepatosplenomegaly with lung disease is the Niemann-Pick A pattern.
D: Galactocerebroside and psychosine accumulate in Krabbe disease, a leukodystrophy of irritable, stiff infants with fevers and globoid cells, not organomegaly.
E: Sulfatides accumulate in metachromatic leukodystrophy, which presents with demyelination (weakness, walking problems, neuropathy), not hepatosplenomegaly or a cherry-red spot.

Key takeaways

Ceramide = sphingosine + fatty acid; every sphingolipidosis is a lysosomal block on the way back to ceramide.
Tay-Sachs (hexosaminidase A, GM2): cherry-red spot, startle, no organomegaly. Sandhoff adds viscera.
Niemann-Pick A (acid sphingomyelinase, sphingomyelin): cherry-red spot plus hepatosplenomegaly and lung disease; olipudase alfa treats non-CNS disease.
Gaucher (glucocerebrosidase): splenomegaly, cytopenias, bone crises, Erlenmeyer flask, tissue-paper macrophages; ERT or substrate reduction.
Krabbe (galactocerebrosidase, psychosine, globoid cells) and MLD (arylsulfatase A, sulfatides) are leukodystrophies; MLD now has gene therapy.
Fabry is the X-linked one: α-galactosidase A, Gb3, burning pain, angiokeratomas, kidney, heart and stroke.