Lysosomal Storage Diseases : Types, Causes, Symptoms, Diagnosis and reatment

Overview

A group of more than 50 rare diseases that causes toxic buildup and damage to the body’s cells and organs is known as lysosomal storage diseases (LSDs). These diseases primarily affect the lysosome – a crucial structure in cells that help break down proteins, carbohydrates, and old cells, so the body can efficiently reuse the same. Patients with LSDs have missing enzymes that assist the lysosome breakdown substances. Therefore, these substances build up in the cells and become toxic. This leads to damaged cells and organs.

The blog explains lysosomal storage diseases, their causes, types, symptoms, and treatment options. 

What are lysosomal storage diseases?

As mentioned above, when an enzyme in  lysosomes is not present, breaking down proteins, carbohydrates, and old cells becomes difficult, accumulating substances in the cell and creating toxicity,  damaging the cells and organs. Treatment options are based on the type of LSDs, including enzyme replacement therapy, stem cell transplants, and medications.

What are the different types of lysosomal storage diseases?

Studies have found more than 50 lysosomal storage diseases, and the identification of more such conditions is continuing. The classification of these diseases is based on the enzyme the patient lacks. They are three broad categories. 

Lipidoses

When the body lacks the enzyme to break down fats, the following specific conditions occur: 

• Cholesteryl ester storage disease
• Wolman disease

Mucopolysaccharidoses

When enzymes that help the body break down complex sugar molecules, known as glycosaminoglycans are missing , mucopolysaccharidoses occurs. The condition includes the following:

• Hunter’s disease
• Hurler’s disease 
• Scheie syndrome
• Hurler-Scheie syndrome
• SanFilippo Syndrome
• Morquio syndrome
• Maroteaux-lamy syndrome
• Sly syndrome

Sphingolipidoses

When there are insufficient enzymes that  break down fatty substances, it causes sphingolipidoses. These enzymes are also responsible for performing specific cell functions, such as protecting the surface of the cells. The following are the conditions: 

• Fabry disease
• Gaucher disease
• Krabbe disease 
• Metachromatic leukodystrophy
• Niemann-pick disease
• Sandhoff disease 
• Tay-Sachs disease
• Gangliosidosis
• Multiple sulfatase deficiency

Other types of LSDs

• Batten disease
• Cystinosis
• Danon disease 
• Pompe disease
• Lysosomal Acid Lipase deficiency infantile and childhood/adult types

What are the causes of lysosomal storage diseases?

Most lysosomal storage diseases are genetic metabolic disorders –a mutated gene is passed down to the children from each parent. A parent may be a carrier of the mutated gene but not show signs or symptoms of any diseases. It is imperative to note that children of both parents with mutated genes have:

• 1 in 4 chances of not inheriting the mutated gene
• 1 in 4 chance of suffering from an LSD
• 1 in 2 chance of being a carrier but not developing an LSD

In some instances, only one parent may have the gene mutation called x-linked inheritance. There are three conditions connected to this mutated gene:

• Danon disease
• Fabry disease
• Hunter’s disease

Sometimes, lysosomal storage diseases may also be caused due to the following:

• Inflammation
• Adverse interaction between the metabolic byproducts and the body

Diseases such as Gaucher and Tay-Sachs develop in people of European and Jewish descent. 

What are the symptoms of lysosomal storage diseases?

The symptoms vary based on the type and the affected cells or organs. The common symptoms are as follows:

• Enlargement of organs in the abdomen region, such as kidneys, liver, pancreas, spleen, and stomach
•  Skeletal muscle changes
• Uneven facial features such as a bulging forehead, flat nose, and large lips 
•  Developmental delays 

It is important to note that each condition has different symptoms. Some of them are mentioned below. 

• The symptoms of Fabry disease are as follows:

• Experiencing pain, numbness, tingling, or burning sensation in the hands and feet
• Body pain
• Fever
• Fatigue
• Skin sores that are red or purple
• Sweating 
• Swelling in the lower legs, ankles, and feet
• Diarrhea, constipation, or both
• Breathing issues 
• Tinnitus and hearing loss
• Dizziness 
• Arrhythmia, heart attacks, and stroke
• Clouding of the cornea
• The symptoms of Gaucher disease are as follows:

• Low red blood cell count
• Enlarged spleen and liver
• Fatigue
• Pain in the bone 
• Fragile bones that fracture easily 
• Pain in the joints
• Eye issues
• Seizures 
• Bleeds and bruises easily

The following symptoms are for Krabbe disease:

• Muscle weakness
• Stiffness in the limbs
• Walking problems
• Loss of vision and hearing 
• Muscle spasms
• Seizures

The symptoms of metachromatic leukodystrophy are as follows:

• No feeling in the hands and feet
• Seizures
• Walking issues 
• Loss of hearing , speech and vision

Symptoms of mucopolysaccharidosis are as follows:

• Short stature and stiff joints
• Speaking and hearing difficulties
• Constant runny nose
• Learning difficulties
• Joint problems 
• Breathing difficulties
• Depression

The following are the symptoms of Niemann-Pick disease:

• Heart diseases
• Enlarged liver and spleen
• Difficulty moving eyes upward and downward
• Jaundiced skin
• Developmental issues
• Troubled breathing

A person suffering from Pompe disease may experience the following symptoms:

• Severe muscle weakness and low muscle tone
• An enlarged liver, heart, or tongue
• Slow growth progress and weight gain in infants

If the doctor suspects a person may be suffering from Tay-Sach disease, the following symptoms are presented:

• Vision and hearing issues 
• Presence of a red spot at the back of the eye
• Seizures

When to seek medical help?

People experiencing any of the symptoms mentioned above or patients with LSDs should seek immediate medical help. Various treatment options will be presented to the patient. 

Request an appointment at Apollo Hospitals      

How are lysosomal storage diseases diagnosed?

Typically, healthcare providers diagnose lysosomal storage diseases during pregnancy. The prenatal screening tests include amniocentesis and chorionic villus sampling. 

Pediatricians screen newborn babies for LSDS with blood tests to detect missing enzymes. The healthcare may use dried blood, collected with a finger prick and blotted on an absorbent paper. 

If the general physician suspects LSD, the patient is referred to an endocrinologist or a pediatric endocrinologist. The following are the tests that are conducted:

• Blood tests: It checks the levels of enzymes
• Genetic testing: Detects mutation in the genes
• Urine tests: Measures the levels of substances that react to enzymes

The doctors also conduct various tests to determine the damage to the organs. The following are the tests: 

• Complete blood count
• Eye exam and hearing test
• Heart examinations, including echocardiogram and electrocardiogram (EKG)
• Kidney and liver function tests
• MRI
• X-rays

Early detection is the key to decreasing the progress of lysosomal storage diseases and improving the patient’s outlook.

What are the treatment options for lysosomal storage diseases?

There is no cure for lysosomal storage diseases. The following are some of the treatment options that slow down the progress of the diseases:

• Enzyme replacement therapy: The doctor delivers the missing enzymes intravenously through this treatment. 
• Substrate reduction therapy: The therapy helps decrease the substances gradually building up in the cells. 
• Stem cell transplant: Donated cells are delivered to the patient to help the body produce the missing enzymes. It can reduce inflammation and tissue damage.
• Gene therapy: This is an experimental therapy. It replaces the mutated genes with healthy genes.
• Pharmacological chaperone therapy (PCT): This therapy sends small molecules that bind to damaged enzymes and improve the function of lysosomes. 

Several other treatment options help manage the symptoms of the disease. These include: 

• Medicines
• Surgery
• Physical therapy
• Dialysis to eliminate toxic substances from the body
• Immunosuppressants
• Nonsteroidal anti-inflammatory drugs
• Orthopedic braces
• Speech therapy

Conclusion

A genetic mutation causes lysosomal storage diseases resulting in the buildup of toxic substances in the body’s cells. Without proper treatment, these harmful substance damages cells and organs. Although incurable, timely and effective treatments can manage the symptoms of the disease and improve the quality of life. 

Frequently Asked Questions (FAQs)

How can one reduce the risk of LSD?

The risk of lysosomal storage disease is not preventable. Therefore, seeking prompt medical treatment helps manage the symptoms and improve the quality of life.

How common is LSD?

LSD is a rare group of diseases that affects 1 in every 40,000 to 60,000 people.

Who is at risk of developing LSD?

Anyone can develop LSD. However, certain ethnic groups are more prone than others. People in eastern Europe, Jewish descendants, and natives of Finland are at a greater risk of certain types of lysosomal storage disease.