NPC2

Niemann-Pick Disease, Type C2

Clinical Characteristics
Ocular Features: 

The primary ocular feature of type C2 Niemann-Pick disease is supranuclear gaze palsy.  A cherry red spot is rarely seen. 

Systemic Features: 

Neurodegeneration is the outstanding clinical manifestation and often the cause of death.  The onset usually occurs in infancy and the course is rapid with death often in the first year of life.  The clinical disease is similar to that of the more common type C1 (257220) although there is considerable clinical heterogeneity in all types of NPC.  Pulmonary involvement can be a prominent feature of C2 disease.  Other neurologic symptoms include ataxia, facial dyskinesis, bradykinesia, expressive aphasia, dysarthria and cognitive decline.  Visceromegaly seems to be less common than in type C1 (257220).  Cholesterol esterification is impaired with accumulation in intracellular organelles. 

Genetics

Like other types of NPC disease, this disorder follows an autosomal recessive pattern of inheritance.  It results from mutations in the NPC2 gene (14q24.3).  These mutations are far less common than those in the NPC1 (257220)gene.  

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Treatment is available for symptoms such as seizures and dystonia.  Good pulmonary hygiene is important and precautions should be taken to prevent aspiration. 

References
Article Title: 

Niemann-Pick Disease, Types C1 (D)

Clinical Characteristics
Ocular Features: 

The predominant ocular sign in types C1 is difficulty in upgaze described as a supranuclear palsy.  Abnormal saccadic movements have been reported as well.  Retinal signs such as a cherry red spot are not common.

Systemic Features: 

Hepatosplenomegaly and cognitive decline are similar in nature to those found in Niemann-Pick disease types A and B.  Types C1 and C2 are clinically similar but discussed separately as they are caused by mutations in separate genes.  Type D is caused by the same mutation causing C1.  Onset of disease manifested by ataxia, seizures and spasticity is usually between 2 and 4 years.  Dystonia, intention tremor, dysarthria, and hepatosplenomegaly are other features but visceral involvement may be absent.  Ascites and jaundice are sometimes present.  Dementia and extrapyramidal signs are often seen later.  However, there is considerable variation in onset and progression of disease but the symptoms are generally milder than that in types A and B.

Genetics

Type C1 (and D) are caused by mutations in the NPC1 gene (18q11-q12), and type C2 (607625) by mutations in the NPC2 gene (14q24.3).  Mutations in C1 are far more common (95%) than C2 mutations.  The gene mutations reduce the efficiency of sphingosine efflux from lysosomes and late endosomes as a result of a defect in esterification of cholesterol.

Types A (257200) and B (607616) Niemann-Pick disease generally cause more severe clinical signs and are the result of a sphingomyelinase deficiency.  All types of Niemann-Pick disease follow autosomal recessive patterns of inheritance.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

It has recently been reported that intrathecal 2-hydroxypropyl-beta-cyclodextrin slows progression of clinical symptoms and prolonged lifespan.

References
Article Title: 

Intrathecal 2-hydroxypropyl-β-cyclodextrin decreases neurological disease progression in Niemann-Pick disease, type C1: a non-randomised, open-label, phase 1-2 trial

Ory DS, Ottinger EA, Farhat NY, King KA, Jiang X, Weissfeld L, Berry-Kravis E, Davidson CD, Bianconi S, Keener LA, Rao R, Soldatos A, Sidhu R, Walters KA, Xu X, Thurm A, Solomon B, Pavan WJ, Machielse BN, Kao M, Silber SA, McKew JC, Brewer CC, Vite CH, Walkley SU, Austin CP, Porter FD. Intrathecal 2-hydroxypropyl-v-cyclodextrin decreases neurological disease progression in Niemann-Pick disease, type C1: a non-randomised, open-label, phase 1-2 trial. Lancet. 2017 Aug 10. pii: S0140-6736(17)31465-4. doi: 10.1016/S0140-6736(17)31465-4. [Epub ahead of print].

PubMed ID: 
28803710

Niemann-Pick disease type C

Vanier MT, Millat G. Niemann-Pick disease type C. Clin Genet. 2003 Oct;64(4):269-81. Review.

PubMed ID: 
12974729
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