Lysosomal Storage Disorders:

Though storage disorders are rare, collectively the incidence is 1:6000 in Western countries while in India this may be higher due to ethnical variation.

Our study of nearly 600 children with developmental regression, hepatosplenomegaly, neuroregression and skeletal dysplasia shows that 33% of such children may have storage disorder. It is likely that every year almost 6000 to 8000 children are born with storage disorders in India, most of which remain undiagnosed due to lack of awareness, limited option for treatment and facility of diagnosis. Although with recent availability of enzyme replacement therapy for disorders like MPS, Fabry, Gaucher, NPD and Pompe there is a growing interest among clinicians to diagnose these cases at an early age.

At FRIGE – IHG, we have the facility to test large number of lysosomal enzymes which are specific for various lysosomal storage disorders.

When to suspect a child with LSD’s?

Children with dysmorphic features, failure to thrive, regression of learned skills, corneal clouding, hepatosplenomegaly, cherry red spot, hearing loss, neuroregression, skeletal dysplasia, respiratory distress with muscular myopathy, and cardiomegaly are at the high risk of storage disorder and need further study of enzymes.

Which investigation to do for LSD’s?

There is no common screening test except plasma chitotriosidase which is markedly elevated in children with Gaucher disease and Niemann Pick A/B type diseases, qualitative and quantitative analysis for GAG from urine for MPS and I cell screen from plasma for I-cell disease. However final confirmation is needed by lysosomal enzyme study either from leucocytes, plasma or fibroblasts.

SCREENIG FOR VARIOUS LSD’s
I-Cell Screening	Mucolipidosis II
Plasma Chitotriosidase	Gaucher’s/NPD
MPS Screening
Azure A Spot test	MPS I – VII
GAG Quantitative analysis	MPS I – VII
GAG Qualitative analysis	MPS I – VII
(MPS electrophoresis)

ENZYMES	DISORDER
Mucopolysaccharidosis
Alpha- Iduronidase	Hurler Syndrome, MPS I
Alpha- Iduronate Sulphate	Hunter Syndrome- MPS II
Heparan N-sulfatase	Sanfilippo Syndrome, MPS IIIA
Plasma N- Acetyl- A- D- Glucosaminidase	Sanfilippo Syndrome, MPS IIIB
Beta-Galactosidase-6-Sulphate-Sulphatase	Morquio Syndrome, MPS IVA
Beta - Galactosidase	Morquio Syndrome, MPS IVB
Arylsulfatase B	Maroteaux-Lamy Syndrome, MPS VI
Beta- Glucuronidase	Sly Syndrome, MPS VII

Glycoproteins degradation
Alpha- Fucosidase	Fucosidosis
Alpha- Mannosidase	Mannosidosis

Glycolipids and lipids
Beta - Galactosidase	GM1 Gangliosidosis
Hexosaminidase (Total)	GM2 Gangliosidosis
Hexosaminidase (A)	GM2 Gangliosidosis
Sphingomyelinase	Niemann Pick Disease A & B
Beta - Glucosidase	Gaucher's Disease

Sulphatides
Arylsulfatase A	Metachromatic Leucodystrophy, MLD
Beta-Galactocerebrosidase	Krabbe Disease

Glycogen Storage
Alpha - 1,4 Glucosidase	Pompe Disease, GSD II
(With/without acarbose)

Globotriaosylceramide
Alpha - Galactosidase	Fabry's Disease

Defects in protein degradation
Tripeptidyl Peptidase	Late infantile Ceroid lipofuscinosis II
Palmitoyl-protein thioesterase	Infantile Ceroid lipofuscinosis I

Defects in degradation of triglycerides and cholesteryls ester
Acid lipase	Wolman disease

Defects in lysosomal transporters
Sialic Acid	Sialic Acid Storage Disorder

Defects in lysosomal trafficking proteins
NPC1	Niemann Pick type C
FRIGE also offers different panel study for LSD’s.

Enzymes in the NEURODEGENERATIVE (and other) screens which can be assayed initially on plasma:

Enzyme:Disorder:
Arylsulphatase A	I-cell
alpha-fucosidase	Fucosidosis
beta-glucuronidase	MPS VII
Total beta-hexosaminidase	Sandhoff
beta-hexosaminidase A	Tay Sachs/ B1 variant
alpha-mannosidase	alpha-mannosidosis
Chitotriosidase	Gaucher disease
	also helpful indicator of other LSD
Enzymes in the NEURODEGENERATIVE (and other) screens which can be assayed initially on leucocytes

Enzyme	Disorder
Arylsulphatase A	Metachromatic leucodystrophy
Galactocerebrosidase	Krabbe leucodystrophy
Beta-galactosidase	GM1 Gangliosidosis
Palmitoyl protein thioesterase	Infantile (INCL)
Tripeptdyl peptidase I	Late infantile (cLINCL)
	neuronal ceroid lipofuscinosis

DYSMORPHOLOGY SCREEN
(send an urine sample as well)
Enzyme	Disorder
beta-galactosidase	GM1 gangliosidosis
Arylsulphatase A	Multiple sulphatidosis
alpha-fucosidase	Fucosidosis
alpha-mannosidase	alpha-mannosidosis
alpha-neuraminidase	Sialidosis
beta-galactosidase	Galactosialidosis
I-cell screen	I-cell (Mucolipidosis II)
beta-glucuronidase	MPS VII – Sly
+Chitotriosidase

LIVER & SPLEEN SCREEN
Enzyme	Disorder
beta-glucosidase	Gaucher disease
Sphingomyelinase	Niemann Pick A and B
beta-galactosidase	GM1 gangliosidosis
alpha-fucosidase	Fucosidosis
alpha-mannosidase	alpha-mannosidosis
alpha-neuraminidase	Sialidosis
I-cell screening	I-cell (Mucolipidosis II)
beta-glucuronidase	MPS VII – Sly
beta-mannosidase	beta-mannosidosis
+ Chitotriosidase

CHERRY RED SPOT & NEUROREGRESSION SCREEN
Enzyme	Disorder
b-hexosaminidase Total/A	GM2 gangliosidosis
Sialic acid (Total & Free): Urine	Sialic acid storage disorder
beta-glucosidase	Gaucher’s disease
Sphingomyelinase	Niemann Pick disease (A/B)
beta-galactosidase	GM1 gangliosidosis
Which samples are needed? Most of the enzyme study is done from leucocytes, fibroblasts or plasma samples. It require about 5 – 8 cc blood in EDTA vial. We also request to send us 10-15 cc of urine and clear plasma as well for additional study.

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Storage Disorder	Enzyme Deficiency	Clinical Features
Niemann-Pick disease, Type A	Sphingomyelinase	Neuropathic, foamy histiocytes in bone marrow, acute neuropathic progressive loss of motor and intellectual capacity early in life, hepatosplenomegaly, cherry-red macula, commonly fatal in infancy
I. SPHINGOLIPIDOSES
Niemann-Pick disease, Type B	Sphingomyelinase	Similar to Niemann-Pick disease, Type A but non-neuropathic and age of onset is slightly older
Niemann-Pick disease, Type C	Depressed cholesterol esterification and abnormal filipin staining; Sphingomyelinase may be depressed but not absent.	Psychomotor symptoms occurring in first year or 2 of life. Vertical supranuclear ophthalmoplegia; hypertonic limbs and loss of coordination; organomegaly common, neonatal hepatitis and/or jaundice; mixed expression due to greater or lesser secondary liver involvement such that milder forms may be considered as described below as subacute.
Gaucher disease	beta-Glucosidase	Type 1—Chronic non-neuropathic: hepatosplenomegaly, Gaucher cells, anemia, bone pain and lytic lesions, striking elevation of angiotensin converting enzyme. Most frequently occurring storage disease with the highest incidence in Ashkenazi Jews.
	beta-Glucosidase	Type 2—Infantile acute neuropathic, rapidly degenerative central nervous system manifestations, peripheral symptoms similar to type 1 but greatly exaggerated, death usually occurs by 1 year of age.
	beta-Glucosidase	Type 3—Subacute neuronopathic; similar to type 2 except later onset and a milder course eventually causing death in early childhood.
Krabbe disease	Galactosylceramide beta-galactosidase	A number of forms are recognized, differing largely in age of onset and severity of symptoms, progressive psychomotor retardation, globoid cells in central nervous system, spastic quadriparesis, hypertonicity, hyperthermia, elevated cerebrospinal fluid protein.
Metachromatic leukodystrophy (MLD)	Arylsulfatase A	Several closely related disorders with differing ages at onset from 1 year of age well into adulthood, peripheral neuropathy, intermittent pain in arms and legs with eventual difficulty sitting, gait disturbance, absence of deep tendon reflexes, plantar flexion of feet. Adult form—slowly progressive dementia; often confused with nonorganic psychoses.
Fabry disease	alpha-Galactosidase	Severe pain in extremities; angiokeratoma on buttocks and around navel; tortuous, dilated conjunctival and retinal venules; neuropathy; hypertension; myocardial ischemia. Female carriers may show manifestations.
Tay-Sachs disease	Hexoaminidase A	Early motor weakness, psychomotor deterioration after 1 year of age, progressive deafness, blindness, startle response, red macula.
Sandhoff disease	Hexosaminidase A and B	Similar to Tay-Sachs but with mild peripheral neuropathy and organomegaly.
GM1 gangliosidosis	beta-Galactosidase	Type 1—Severe mental retardation, seizures and muscle hypotonicity apparent in first few months of life, dysostosis multiplex, foam cells in marrow.
	beta-Galactosidase	Type 2—Regression of normal motor development apparent after age 1, seizures and rapidly progressive spasticity after first symptoms apparent, mild dysostosis multiplex.
II. MUCOPOLYSACCHARIDOSES (MPS)
Hurler syndrome (MPS IH)	alpha-L-Iduronidase	Progressive mental and physical debilitation beginning at age 1, corneal opacities, coarse facies, gingival hyperplasia, dysostosis multiplex, stiff joints (claw-hands), dwarfing, organomegaly.
Scheie syndrome (MPS IS)	alpha-L-Iduronidase	A mild form of MPS IH with corneal opacity, mild or absent mental retardation, claw-hand deformity, aortic stenosis.
Hunter syndrome (MPS II)	Iduronate sulfatases	Dysostosis multiplex essentially the same as in MPS IH, mental retardation in the severe forms (syndrome runs gamut from severe to mild). Lack of corneal clouding; there is a longer life span of even the severest form.
Sanfilippo syndrome (MPS IIIa)	Heparan N-sulfatase	Behavioral problems progressing to severe mental retardation, comparatively mild or nonexistent connective tissue abnormalities, pronounced hirsutism. Type a is the most common of the Sanfilippo’s syndromes.
Sanfilippo syndrome (MPS IIIb)	alpha-N-Acetylglucosaminidase	Indistinguishable clinically from MPS IIIa.
Sanfilippo syndrome (MPS IIIc)	alpha-Glucosaminide-N-acetyltransferase	Indistinguishable clinically from MPS IIIa.
Sanfilippo syndrome (MPS IIId)	N-Acetylglucosamine-6-sulfate sulfatase	Indistinguishable clinically from MPS IIIa.
Morquio disease (MPS IVa)	Galactosamine-6-sulfate sulfatase	Pronounced skeletal anomalies with small stature (short-trunk dwarfism), short neck, prominent lower ribs, odontoid anomalies, normal intellect.
Morquio disease (MPS IVb)	beta-G alactosidase	Mild form of IVa, spondyloepiphyseal dysplasia, short stature, cloudy corneas, normal intellect.
Maroteaux-Lamy disease (MPS VI)	Arylsulfatase B	Severe-mild dysostosis multiplex, gross corneal opacity, retardation of growth, normal intellect, cardiomyopathy.
Sly disease (MPS VII)	beta-Glucuronidase	Mild mental retardation, somewhat coarse facies, gingivitis, organomegaly, sometimes with corneal clouding.
III. DISORDERS OF UNDEFINED GLYCOPROTEIN AND/OR LIPID STORAGE PRODUCTS
Fucosidosis	alpha-Fucosidase	Type 1—Frequent respiratory infections, progressive psychomotor retardation, dysostosis multiplex (“Hurler-like”), thick skin with hypersecretion of sweat with elevated salinity, cardiomegaly.
	alpha-Fucosidase	Type 2—Distinguished from type 1 by its milder clinical presentation and absence of unusual sweating; lesions (angiokeratoma) can be present.
Mannosidosis	alpha-Mannosidase	Mild hepatosplenomegaly, mild radiologic bone changes, psychomotor retardation, nerve deafness.
Mucolipidosis I (ML I) (sialidosis)	Neuraminidase and after beta-galactosidase deficiency	Type I—(Normomorphic) Cherry-red spots of the macula, myoclonus, normal intelligence.
	Neuraminidase	Type II—(Dysmorphic) Dysostosis multiplex, mental retardation, myoclonus, cherry-red spots of the macula, both infantile and juvenile onset.
IV. DISORDERS PRESUMED TO INVOLVE MULTIPLE mmmb STORAGE PRODUCTS
Mucolipidosis II (ML II) (I-cell disease)	UDP-N-acetylglucosemia: glycoprotein N-acetylglucosaminyl-phosphotransferase	Early onset of Hurler-like symptoms (often noted at birth), gingival hyperplasia, thoracic deformities, hepatosplenomegaly.
Mucolipidosis III (ML III) (pseudo-Hurler polydystrophy)	UDP-N-acetylglucosemia: glycoprotein N-acetylglucosaminyl-phosphotransferase	Mild variant of ML II; slowly progressing Hurler-like features, particularly claw-hand deformity; mild growth and mental retardation; joint stiffness with reduced mobility.
Multiple sulfatase deficiency (MSD)	Deficiency of all lysosomal sulfatases to greater or less degrees (arylsulfatase A less than arylsulfatase B).	Similar to infantile metachromatic leukodystrophy but with the skeletal anomalies of mucopolysaccharidoses, hepatosplenomegaly, thickening of the skin, ichthyosis.
Schindler disease	alpha-N-Acetylgalactosaminidase (?-galactosidase B)	Onset at about 1 year followed by development delay, and thereafter, psychomotor retardation, cortical blindness, spasticity, decorticate posturing.
V. GLYCOGEN STORAGE DISORDERS
Pompe disease (Type II GSD)	alpha-Glucosidase (acid maltase)	Though glycogen storage is ubiquitous to nearly all tissues, cardiomegaly and hypotonia are the most life-threatening of the sequelae. There are multiple forms of the disease which give rise to infantile through adult presentation.