What Are The Types Of Niemann Pick Disease & How Is It Inherited?

Niemann Pick disease is a rare genetic disorder, which happens due to the absence of an enzyme called sphingomyelinase. This enzyme is responsible for fat metabolism and its absence causes some organs to overload with fats.

Niemann Pick disease is a disease that occurs in three distinct types: A, B, and C. The first two types are caused by a deficiency of lysosomal acid sphingomyelinase, a specific enzyme, which causes a cluster of sphingomyelin and cholesterol in monocytes. There was previously a Type D but later found to be a variant of Type C. Another Type E is also present, which is very rare and affects adults.(1)

What Are The Types Of Niemann Pick Disease?

What Are The Types Of Niemann Pick Disease?

Type A form of Niemann Pick disease causes neurological disorders. Type B corresponds to Niemann Pick disease without neurological manifestation. Niemann Pick disease type C disease refers to a lysosomal disease due to an accumulation of non-esterified cholesterol.

Type A and B are referred to as Type 1. Type C is referred to as Type 2.(1) (2)

There are primarily 3 types of Niemann Pick disease, Type A, B, C, and E. All these diseases are hereditary and there is little to no cure. Only symptomatic relief can be provided with measures to delay the progression of the disease. All the types are life-threatening and patients usually die within one year of the onset of symptoms.

Causes And Symptoms Of Niemann Pick disease

Niemann Pick disease results from a deficiency of an enzyme, sphingomyelinase. This anomaly leads to cholesterol overload and a whole series of clinical manifestations that vary according to the form of the disease.

Sphingomyelinase can break down (metabolize) a fatty substance called sphingomyelin, which is found in every cell of your body. When sphingomyelinase is missing or not functioning properly, sphingomyelin accumulates inside the cells. This leads to cell death and makes it difficult for organs to function properly. Type A occurs in all races and ethnicities, but higher rates are observed among Ashkenazi (Eastern Europe) Jewish population.

Typ C Niemann Pick disease occurs when your body cannot break down cholesterol and other fats (lipids). This leads to too much cholesterol in the liver and spleen and excessive amounts of other lipids in the brain. There may be reduced sphingomyelinase activity in some cells. Type C Niemann-pick of the disease has been reported in all ethnic groups, but it is more common among Puerto Ricans of Spanish descent.

Type D Niemann Pick disease involves a defect that interferes with the movement of cholesterol between brain cells. It is now considered a variant of Type C. This type of Niemann-pick of disease was observed among the French-Canadian population.

There is also an adult-onset form of Niemann Pick disease, which is sometimes called the Type E of the disease. It appears from early childhood and is manifested by an increase in the volume of affected organs, mainly spleen and liver, digestive disorders, edema, and abnormalities in psychomotor development.

Common symptoms of the disease include digestive disorders, edema, enlarged liver and spleen, and breathing problems. However, symptoms vary according to the type of disease.

Symptoms of Type A and B Niemann-pick usually begin in the first months of life. Type C usually affects school-age children, but the disease can occur at any time between infancy to adulthood, while the Type E symptoms appear during adulthood.(4)

Diagnosis Of Niemann Pick disease

Blood tests are done, where the amounts of cholesterol and other blood lipids are greatly increased in diseased individuals. Type A and B are diagnosed by measuring the amount of sphingomyelinase in white blood cells. These tests can tell who has the disease but does not reveal who can be carriers. DNA tests can be done to diagnose carriers of type A and B. A skin biopsy is usually used to diagnose Type C Niemann-pick disease.(1)

Treatment For Niemann Pick disease

The treatment for Niemann Pick disease is symptomatic; it varies according to the patient’s disorders. There is no specific cure presently available for the disease, particularly for Type A. The bone marrow transplant was performed on a small number of patients with Type B with encouraging results. Researchers continue to study possible treatments, including enzyme replacement therapy and gene therapy. Type C has in recent times been authorized for a fresh therapy known as miglustat. In its severe form, death usually occurs in the first years of life.(5)

References:  

  1. Vanier MT. Niemann–pick diseases. Handbook of clinical neurology. Vol 113: Elsevier; 2013:1717-1721.
  2. Schuchman EH, Desnick RJ. Types a and B Niemann-pick disease. Molecular genetics and metabolism. 2017;120(1-2):27-33.
  3. Vanier MT. Complex lipid trafficking in Niemann-Pick disease type C. Journal of inherited metabolic disease. 2015;38(1):187-199.
  4. Pineda M, Juríčková K, Karimzadeh P, et al. Disease characteristics, prognosis and miglustat treatment effects on disease progression in patients with Niemann-Pick disease Type C: an international, multicenter, retrospective chart review. Orphanet journal of rare diseases. 2019;14(1):32.
  5. Pineda M, Walterfang M, Patterson MC. Miglustat in Niemann-Pick disease type C patients: a review. Orphanet journal of rare diseases. 2018;13(1):1-21.

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