- 1 Definition
- 2 Disease Cause
- 3 Occurrence
- 4 Symptoms
- 5 Examinations
- 6 Diagnosis
- 7 Treatment
- 8 Different types of storage disorder
- 9 Other storage diseases
- 10 Literature
Storage diseases are often part of the group called Lysosomal Storage Diseases (LSD). This is a group of diseases that includes approx. 50 more or less rare diagnoses. Common is that they are genetically (hereditary) conditioned. Some cases occur spontaneously by mutation. In case of a metabolic defect, large molecules (macromolecules) in the body's organs and displaces normal tissues. Thus, the function of the affected organs is gradually reduced. The different storage diseases can be partly distinguished by attacking different organs. Common is often damage to the liver, spleen and heart, in some cases the brain. Most storage diseases are detected in early childhood. Some of the storage disorders may be reminiscent of rheumatic disease to begin with, including connective tissue disorders (Reference James RA, 2016). Mitochondrial disease which are also considered among the metabolic are discussed on a separate page.
The cause of the disease is a lack of important enzymes that should have been produced in the cells lysosomes. In each condition, it is usually a single enzyme that does not work normally. Thus, different types of disease occur.
Lysosomal diseases are estimated to attack approx. 1/7000 newborns. Some of the diagnoses are found almost exclusively in some ethnic groups or in specific geographical areas.
The diseases have different ages at the onset of symptoms. Some debut even before birth or very early after birth. Others show up during childhood or (less frequently) in adults. different severity and attacks different organs.
Some disease traits among children with storage disease:
- Delayed development
- Growth failure
- Increasing size of liver and spleen
- Increasing belly circumference
- Gradually heart failure
- Striking heavy breathing at physical stress
- Fluid in the legs
- Cold, bluish hands
- Reduced hearing and sight
- Seizures (epilepsy-like)
Prenatal examination / screening (during pregnancy) is possible. Later, serum and urine tests for lysosomal storage diseases can be performed.
Medical history includes typical symptoms (see above), previous miscarriages, and hereditary predispositions.
Clinical signs of deviations from normal development and typical disease traits are considered (see diagnoses below). Changes in eyes, auditory organs, face, skin, joints, skeleton, back, heart, lungs and abdomen (liver and spleen) are noted.
Laboratory tests may include CRP, SR, hgb, leukocytes with differential counts, platelets, electrolytes, liver, kidney, and thyroid function tests, glucose, creatine kinase CK. Differential diagnostics, ANA may be relevant. Urine sticks. Special enzyme defects can also be detected in blood samples.
Imaging such as ultrasound of the abdominal area (liver, spleen, kidneys), X-ray and MRI examinations for symptoms. Other: Cardiac examination with ECG and echocardiography relevant. Hearing can be assessed by audiometry. An ophthalmologist can assess vision. Lung function tests can be done in older children.
When the symptoms give rise to suspicion of storage disease or hereditary disposition, blood tests are being investigated for enzyme deficiency. In special cases, analyzes of genes can also be done.
The treatment options are different for the different storage diseases. In some cases it is used stem cell transplant (from bone marrow or umbilical cord blood) or supplementation of the missing enzymes. Enzyme replacement. This is the most commonly used treatment at the moment, but not for all types. Enzyme replacement can be used in Gaucher, Fabry, Pompe and Wolman disease, α-mannosidosis, NCL type 2, and mucopolysaccharidosis type I, II, IV, VI and VII.
However, treatment is not curative. It is being researched on gene therapy which can cure the diseases. Unfortunately, many still die children with storage illness within months to years.
Different types of storage disorder
The various storage diseases can be divided according to the type of molecules that are incorrectly stored in the body. Each disease group has in part many subgroups that make up the 49 known diseases. Many are listed in the reference (Reference: Wikipedia 2018). Here are the main groups:
Cystinosis (Amino acid defect)
The disease results in reduced transport of the amino acid cystine out of the lysosomes in the cells. Among children, cystinosis is the most common cause of Fanconi's syndrome. Cystinosis comes in three different forms, of which the kidney type (nephropathic) starts during the first year of life, the intermediate type begins in the teens and an adult type that has only eye manifestations.
Glycoprotein storage disease (Mucolipidoses)
Mucolipidoses consist of several types that have clinical and blood test changes that are similar to both mucopolysaccharides and sphingolipidoses. The cause is accumulation of glycoproteins and glycolipids. Type I (sialidosis) is caused by a lack of sialidase encoded by the gene NEW1 (6p21.33). Type II (I-cell disease) and III (pseudo-Hurler) are due to a lack of N-acetylglucosaminyl phosphotransferase encoded by the gene GNPTAB (12q23.2). Type IV is caused by mutations in MCOLN1 the gene (locus 19p13.2-13.3) that encodes the lysosomal membrane channel and is involved in Ca2+ signaling.
Glycogen storage disease type II (Pompe Disease)
Pompe is a genetic neuromuscular disease. The disease is also detected in adults, partly due to delayed diagnosis. The cause of Pompe is a lack of the enzyme acid α-glucosidase, which means that glycogen is not metabolised in the cells and stored intracellularly in the lysosomes, especially in muscle cells. The error is in GAA gene (17q25.3). Symptoms include muscle weakness with cardiac and pulmonary failure.
Definition. Mucopolysaccharidosis is a group storage diseases which are characterized by absence or too low activity in lysosomal enzymes in the cytoplasm of the cells. Thus, glycosaminoglycans (synonym: mucopolysaccharides) do not break down. Accumulation of glycosaminoglycans in the cells causes damage to the skeleton, cartilage, tendons, nervous system, eyes (cornea), skin and connective tissue generally in the body. The diseases are genetic (hereditary) caused and separated autoimmune connective tissue disease. The course of the disease is different between the different types. Type I (Hurler disease, Scheie), type II (Hunter syndrome), type III (Sanfilippo), type VI (Maro-teaux - Lamy), type VII (Sly) and type IX (hyaluronidase deficiencies) are all characterized by stiffness and contractures of joints. Type IV (Morquio) is dominated by hypermobility. Mucopolysaccharidosis is genetically caused and distinguished from autoimmune connective tissue diseases. The course of the disease is different between the different types.
Symptoms. The different types of mucopolysaccharidosis have similar symptoms, but to varying degrees; Gradual development over the first years of life, facial features with low nasal ridge, thick lips, large mouth and tongue, short upper body, thickened skin, large stomach, increased hair growth on the body.
Investigational Findings; large liver and spleen, urine tests, increased amount of polysaccharidosis, enzyme essay tests in blood (age-dependent reference ranges) Prenatal fetal diagnosis is possible.
Different types of mucopolysaccharidosis (MPS type I - IX):
- MPS Type I includes Hurler, Hurler-Scheie og Scheie syndrome
- MPS Type II, (Hunters syndrome)
- MPS Type III, (Sanfilippo syndrome), divided into type A-D
- MPS Type IV, (Morquio syndrome)
- MPS Type V, corresponds to Type I in the form of Scheie syndrome
- MPS Type VI, (Maroteaux-Lamy syndrome)
- MPS Type VII, (Sly syndrome)
- (MPS, Type VIII is taken out of classification because it is covered by the other types)
- MPS, Type IX, (Hyaluronidase deficiency)
Similar conditions / Differential diagnoses are mucolipidosis with fat storage and a similar appearance to mucopolysaccharidosis. Other storage diseases (Left-handed , Niemann Pick), Legg-Calve-Pertes Disease (CLP) which causes symptoms from hips, spondylo-epiphyseal dysplasia (SED)
Literature: Muenzer J, 2011
Other storage diseases
- Disease in carbohydrate matabilism
- Illness in amino acid metabolism
- Uric acid cycle defective
- Illness in organic acid metabolism (organic acidurias)
- Illness in fatty acid oxidation and mitochondrial metabolism
- Medium-chain acyl-coenzyme A dehydrogenase deficiency(often shortened to MCADD.)
- Illness in porphyrin metabolism
- Illness in purine or pyrimidine metabolism
- Illness in steroid metabolism
- Illness in mitochondrial function
- Illness in peroxisomal function
- Fabry's disease, lack of alpha-galactosiderase (α-Gal A)
- Lysosomal acid lipase deficiency (LAL-D):
- Autosomal hereditary storage disease where too low production of the enzyme active lysosomal acid lipase. Symptoms: From the first year of life, large stomach, digestive problems, lack of weight gain, reduced growth, yellow-colored skin are seen. Milder forms are diagnosed among young adults. Heart disease, liver failure and stroke can be complications. Treatment consists of adding the enzyme sebelipase-alpha which replaces the missing enzyme. Prenatal fetal diagnosis is possible. Genetic counseling (25% risk of siblings becoming ill). Literature: Wierzbicka-Rucińska A, 2016.