What are Lysosomal Storage Disorders?

Lysosomal storage disorders are a group of more than 50 rare diseases. They affect the lysosome -- a structure in your cells that breaks down substances such as proteins, carbohydrates, and old cell parts so the body can recycle them.

People with these disorders are missing important enzymes (proteins that speed up reactions in the body). Without those enzymes, the lysosome isn’t able to break down these substances.

When that happens, they build up in cells and become toxic. They can damage cells and organs in the body.

This article covers some of the most common lysosomal storage disorders.

Types of Lysosomal Storage Disorders

Each disorder affects a different enzyme and has its own set of symptoms. They include:

Fabry disease: It affects your ability to make alpha-galactosidase A. This enzyme breaks down a fatty substance called globotriaosylceramide. Without the enzyme, this fat builds up in cells and damages them.

Symptoms might include:

• Pain, numbness, tingling, or burning in the hands and feet
• Body aches
• Fever
• Tiredness
• Red or purple skin sores
• Trouble sweating
• Swelling in the lower legs, ankles, and feet
• Clouding of the cornea (the clear cover on the front of the eye)
• Diarrhea, constipation, or both
• Trouble breathing
• Ringing in the ears and hearing loss
• Dizziness
• Abnormal heart rhythms, heart attack, and stroke

Gaucher disease: A lack of glucocerebrosidase (GBA) causes this condition. This enzyme breaks down a fat called glucocerebroside. Without GBA, the fat builds up in the spleen, liver, and bone marrow.

Gaucher disease comes in three types, each with different symptoms. In general, symptoms include:

• Anemia (low red blood cell count)
• Enlarged spleen and liver
• Easy bleeding and bruising
• Tiredness
• Bone pain and fractures
• Joint pain
• Eye problems
• Seizures

Krabbe disease: This affects the nervous system. A lack of the enzyme galactosylceramidase causes this condition. This enzyme helps make and maintain myelin, the protective coating around nerve cells that helps nerves talk to each other.

Symptoms start in the first few months of life and include:

• Muscle weakness
• Stiff limbs
• Trouble walking
• Vision and hearing loss
• Muscle spasms
• Seizures

Metachromatic leukodystrophy (MLD): You can get MLD if you don’t have the enzyme arylsulfatase A. It normally breaks down a group of fats called sulfatides. Without the enzyme, these fats build up in white matter -- the part of the brain that contains nerve fibers. They destroy the myelin coating that surrounds and protects nerve cells.

MLD comes in different forms. Symptoms can include:

• Loss of feeling in the hands and feet
• Seizures
• Trouble walking and talking
• Vision and hearing loss

Mucopolysaccharidosis (MPS): This a group of diseases that affects enzymes that break down certain carbohydrates. The unbroken carbohydrates build up in many different organs.

Symptoms of MPS affect many parts of the body and can include:

• Short height
• Stiff joints
• Trouble speaking and hearing
• Ongoing runny nose
• Learning problems
• Heart issues
• Joint problems
• Trouble breathing
• Depression

Niemann-Pick disease: This is a group of disorders. The most common forms are types A, B, and C.

• In types A and B, people lack an enzyme called acid sphingomyelinase (ASM). It breaks down a fatty substance called sphingomyelin, which is found in every cell.
• In type C, the body can't break down cholesterol and fats in cells. Cholesterol builds up in the liver and spleen. Other fats build up in the brain.

Symptoms of Niemann-Pick include:

• An enlarged liver and spleen
• Trouble moving your eyes up and down
• Jaundice (yellow skin and eyes)
• Slow development
• Breathing problems
• Heart disease

Pompe disease: It affects the enzyme alpha-glucosidase (GAA). This enzyme breaks down the sugar glycogen into glucose. Without GAA, glycogen builds up in muscle cells and other cells.

Symptoms include:

• Severe muscle weakness
• Poor muscle tone
• Lack of growth and weight gain in infants
• An enlarged heart, liver, or tongue

Tay-Sachs disease: This is caused by a lack of the enzyme hexosaminidases A (Hex-A). This enzyme breaks down a fatty substance called GM2 ganglioside in brain cells. Without it, the fat builds up in nerve cells and damages them.

Babies with Tay-Sachs grow normally for the first few months of life. Then their development slows. They lose control over their muscles. It becomes harder for them to sit, crawl, and walk. Other symptoms include:

• A red spot in the back of the eye
• Vision and hearing loss
• Seizures

How Do These Disorders Happen?

Most lysosomal storage disorders are passed down from parents to their children. Usually, a child has to inherit the faulty gene from both parents. If a child gets the gene from only one parent, they will be a carrier and won't show symptoms.

The faulty genes affect how your body makes enzymes that break down material in the cells.

Lysosomal storage diseases are rare, but some forms are more common in certain groups of people. For example, Gaucher and Tay-Sachs happen more often in people of European Jewish descent.

Symptoms

The symptoms depend on which enzyme is missing.

Each of these conditions has different symptoms based on the cells and organs it affects.

Diagnosis

Your doctor can test for these disorders in your baby during blood-tests' target='_blank' rel='noopener noreferrer' >pregnancy. If you have a child with symptoms, blood tests can look for the enzyme that's missing.

The doctor might also do these tests:

• MRI uses powerful magnets and radio waves to make pictures of the brain.
• Biopsyremoves a small piece of tissue, which is checked under a microscope for signs of disease.

Finding these diseases early is key. Treatments can slow lysosomal storage disorders and improve your child's outlook.

Treatments

Though there isn't a cure for lysosomal storage disorders, a few treatments can help.

• Enzyme replacement therapy delivers the missing enzyme through a vein (IV).
• Substrate reduction therapy reduces the substance that is building up in the cells. For example, the drug miglustat (Zavesca) treats one form of Gaucher disease.
• Stem cell transplant uses donated cells to help the body make the enzyme it's missing.

Treatments to manage symptoms of the disease include:

• Medicine
• Surgery
• Physical therapy
• Dialysis (a treatment that removes toxic substances from the body)

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