Niemann–Pick disease

INTRODUCTION:
  • Niemann-Pick disease also know as Sphingomyelinase deficiency is a group of diseases passed down through families (inherited) in which fatty substances called lipids collect in the cells of the spleen, liver, and brain.
  • There are four most commonly recognized forms of the disease: Types A, B, C, and D.
  1. Types A and B are also called Type I.
  2. Types C and D are also known as Type II.
  • Each type involves different organs. It may or may not involve your nervous system and breathing. Each one can cause different symptoms and may occur at different times throughout life.
  • Niemann-Pick disease is autosomal recessive
ETIOLOGY:
  • Niemann-Pick disease types A and B occur when cells in the body do not have an enzyme called acid sphingomyelinase (ASM). 
  • If ASM is missing or does not work properly, sphingomyelin builds up inside cells. This kills your cells and makes it hard for organs to work properly.
  • Neimann-Pick is a disease in which excess material is stored inside cells (metabolic storage disease). These cells are referred to as "foam cells" because of their foamy or soap-suds appearance.
  • Type C occurs when the body cannot properly break down cholesterol and other fats (lipids). This leads to too much cholesterol in the liver and spleen and too much of other lipids in the brain. 
  • Type D involves a defect that interferes with how cholesterole moves between brain cells. It is a variant of type C. 


SYMPTOMS:
  • Type A usually begins in the first few months of life. Symptoms may include:
  1. Abdominal (belly area) swelling within 3 - 6 months
  2. Cherry red spot in the eye
  3. Feeding difficulties
  4. Loss of early motor skills (gets worse over time)
  5. Type B symptoms are usually milder. 
  6. They occur in late childhood or the teenage years. 
  7. Abdominal swelling may occur in young children. 
  8. There is almost no brain and nervous system involvement, such as loss of motor skills. 
  9. Some patients may have repeated respiratory infections.
  • Type C usually affects school-aged children. However, it may occur any time between early infancy to adulthood. Symptoms may include:
  1. Difficulty moving limbs (dystonia)
  2. Enlarged spleen
  3. Enlarged liver
  4. Jaundice at (or shortly after) birth
  5. Learning difficulties and intellectual decline (dementia)
  6. Seizures
  7. Slurred, irregular speech
  8. Sudden loss of muscle tone which may lead to falls (cataplexy)
  9. Tremors
  10. Trouble moving the eyes up and down (vertical supranuclear gaze palsy)
  11. Unsteady gait, clumsiness, walking problems (ataxia)
  • Symptoms of Type D are similar to Type C.
DIAGNOSIS:
  • A blood or bone marrow test can be done to diagnose types A and B. 
  1. The test can tell who has the disease, but does not show if you are a carrier. 
  2. DNA tests can be done
  3. To diagnose carriers of types A and B.
  • DNA tests may also be done to look for the two genes that cause this type
  1. A skin biopsy is usually done to diagnose types C and D. 
  2. The health care provider watches how the skin cells grow, move, and store cholesterol. 
  • Other tests might include:
  1. Bone marrow aspiration
  2. Liver biopsy (usually not needed)
  3. Slit-lamp eye exam
  4. Sphingomyelinase assays
TREATMENT:
  • At this time, there is no effective treatment for type A & D.
  • Bone marrow transplants in type B .
  • Miglustat drug for the nervous system symptoms of type C.
  • A healthy, low-cholesterol diet is recommended
COMPLICATIONS
  • Blindness
  • Brain damage with intellectual disability and delayed development of physical skills
  • Deafness
  • Death
Exam Question
  • A severely retarded infant is noted to have hepatosplenomegaly and a cherry-red spot in the macula is diagnosed to have Niemann-Pick disease
  • A 2 year old retarded child is evaluated by a metabolic specialist. The child's history is significant for failure to thrive and progressive neurologic deterioration, including deafness and blindness. Physical examination is remarkable for hepatosplenomegaly, as well as a cherry-red spot on funduscopic examination. These symptoms are consistent with a diagnosis of Niemann-Pick disease
  • Examination of the fundus shows Cherry red spot in Niemann-Pick disease
  • Accumulation of sphingomyelin in phagocytic cells is feature of Niemann-Pick disease
  • Foam cells seen in Niemann-Pick disease
  • Deficiency of sphingomyelinease causes Niemann-Pick disease
  • Niemann-Pick disease is autosomal recessive
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