Diseases due to Errors in Lipid Metabolism

The following points highlight the six major diseases caused due to errors in lipid metabolism. The diseases are: 1. Gaucher’s Disease 2. Niemann-Pick Disease 3. Tay-Sach’s Disease 4. Fabry’s Disease 5. Refsum’s Disease 6. Krabbe’s Disease.

Errors in Lipid Metabolism: Disease # 1. Gaucher’s Disease:

In this disease, the cerebroside content of the re­ticuloendothelial cells (e.g., spleen) is very high. In the cerebroside molecule, the kerasin is character­ized by glucose replacing galactose.

The concen­trations of cerebrosides are much higher in medullated than non-medullated nerve fibers. The symp­toms of this disease are mentioned below. The dis­ease is caused by the deficiency of glucosyl ceremide hydrolase or glucocerebrosidase.

a. The spleen is significantly increased and there are signs of leukopenia and throm­bocytopenia.

b. The liver is enlarged and the marrow cav­ity is widened.

c. Eyes show a yellow-brown wedge-shaped elevation.

d. In early infantile form, the disease starts early and death occurs before attaining the age of 2 years. Neurological symptoms are usually present.

Errors in Lipid Metabolism: Disease # 2. Niemann-Pick Disease:

In this disease, excessive amounts of sphingomy­elin are deposited in spleen, brain and liver. This results in the deficiency of sphingomyelinase. The hereditary disease is found in infancy and death occurs within the first two years of life.

The clinical findings are:

a. Enlarged liver and spleen.

b. Mental retardation and fatal in early life.

c. Anemia and leukocytosis.

d. The nervous system is affected.

e. A cherry red spot may be seen over the retina.

f. Cholesterol deposits in the tissues are in­creased.

Errors in Lipid Metabolism: Disease # 3. Tay-Sach’s Disease:

This disease is characterized by the increased ac­cumulation of Gangliosides (GM₂) in brain and spleen.

The characteristic clinical symptoms are:

a. Mental retardation, blindness and muscu­lar weakness.

b. A cherry red spot appears in the muscular region of the eye within the first year of life.

c. At about two years of age, the circumfer­ence of the head becomes 50 per cent greater than normal.

d. There is repeated respiratory tract infec­tions of the patient and the patient ex­pires at the third or fourth year.

Errors in Lipid Metabolism: Disease # 4. Fabry’s Disease:

In this disease, large amounts of ceramide trihexoside are accumulated in the kidney. The deficiency of the enzyme ceramide trihexosidase causes this disease.

The clinical findings are:

a. Skin rash and kidney failure.

b. Male patients generally die due to pro­gressive renal failure in the fourth or fifth decade of life.

c. Cardiac enlargement and edema of the ex­tremities.

d. Some patients suffer from excessive pain in the joints.

e. Corneal opacities and vascular dilatation are frequent.

Errors in Lipid Metabolism: Disease # 5. Refsum’s Disease:

This disease occurs due to the accumulation of large amounts of phytanic acid (3, 7, 11, 15-tetramethyl hexadecanoic acid). The deficiency of the enzyme phytanic acid oxidase causes the disease.

The clini­cal symptoms are:

a. The early symptoms are signs of chronic polyneuropathy with distal muscular at­rophy.

b. Severe pain in the knees.

c. The deep tendon reflexes are weak or ab­sent.

d. Night blindness and narrowing of the visual fields.

e. Deafness and anosmia.

f. Cardiac involvement may lead to tachy­cardia.

g. The cerebrospinal fluid protein is always increased while the cell count is normal.

Errors in Lipid Metabolism: Disease # 6. Krabbe’s Disease:

This disease results in the deficiency of galactocerebrosidase which catalyses the hydroly­sis of galactocerebroside to form ceramide and ga­lactose. Galactocerebroside is the important com­ponent of myelin. The clinical manifestation of this disorder is severe mental retardation in infant.

There is nearly total absence of myelin in the central nervous sys­tem which is replaced by gliosis and ‘globoid bod­ies’ appear in the white matter. Diagnosis of the patients depends on the determination of the galactocerebrosidase activity in leukocytes.