Test ID: NPCKM
Niemann-Pick Type C Disease, Known Mutation

Carrier testing of individuals for Niemann-Pick disease type C (NPC) when familial mutations have been previously identified

Diagnostic confirmation of NPC when familial mutations have been previously identified

Prenatal testing when 2 familial mutations have been previously identified in an affected family member

Documentation of the specific familial mutations(s) must be provided with the specimen in order to perform this test.

For prenatal specimens only: If amniotic fluid (non-confluent cultured cells) is received, amniotic fluid culture/genetic test will be added and charged separately. If chorionic villus specimen (non-confluent cultured cells) is received, fibroblast culture for genetic test will be added and charged separately. For any prenatal specimen that is received, maternal cell contamination studies will be added.

• Molecular Genetics-Biochemical Disorders Patient Information Sheet
• Informed Consent for Genetic Testing

Polymerase chain reaction (PCR) followed by DNA sequencing and/or gene dosage analysis by multiplex ligation-dependent probe amplification (MLPA) of NPC1 and NPC2 genes is utilized to test for the presence of mutations previously identified in an affected family member.

(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)

This test can only be performed if a mutation has previously been identified in a family member of this individual.

Forms:

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.

2. Molecular Genetics-Biochemical Disorders Patient Information Sheet (Supply T527) in Special Instructions

3. If not ordering electronically, submit a Molecular Genetics Request Form (Supply T245) with the specimen.

Specimen must arrive within 96 hours of collection.

Submit only 1 of the following specimens:

Specimen Type: Whole blood

Container/Tube:                                  

Preferred: Lavender top (EDTA) or yellow top (ACD)

Acceptable: Any anticoagulant

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred)/Refrigerated

Specimen Type: Cultured fibroblasts

Container/Tube: T-75 or T-25 flask        

Specimen Volume: 1 Full T-75 or 2 full T-25 flasks

Specimen Stability Information: Ambient (preferred)/Refrigerated <24 hours

Due to the complexity of prenatal testing, consultation with the laboratory is required for all prenatal testing. Prenatal specimens can be sent Monday through Thursday and must be received by 5 p.m. CST on Friday in order to be processed appropriately. All prenatal specimens must be accompanied by a maternal blood specimen. Order MCC/88636 Maternal Cell Contamination, Molecular Analysis on the maternal specimen.

Specimen Type: Amniotic fluid

Container/Tube: Amniotic fluid container

Specimen Volume: 20 mL

Specimen Stability Information: Refrigerated (preferred)/Ambient

Specimen Type: Chorionic villi

Container/Tube: 15-mL tube containing 15 mL of transport media

Specimen Volume: 20 mg

Specimen Stability Information: Refrigerated

Acceptable:

Specimen Type: Confluent cultured cells

Container/Tube: T-25 flask

Specimen Volume: 2 Flasks

Collection Instructions: Submit confluent cultured cells from another laboratory.

Specimen Stability Information: Ambient (preferred)/Refrigerated

Specimen Type: Skin biopsy

Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin. Tubes can be supplied upon request (Eagle's minimum essential medium with 1% penicillin and streptomycin [Supply T115]).

Specimen Volume: 4-mm punch                                                       

Specimen Stability Information: Refrigerated (preferred)/Ambient

No specimen should be rejected. If specimen not received at appropriate temperature or in wrong anticoagulant, include note to laboratory. If questions, contact laboratory.

Niemann-Pick type C (NPC) is an inherited disorder of cholesterol transport that results in an accumulation of unesterified cholesterol and lipids in the lysosomal/endosomal system and in various tissues. Although NPC belongs to a group of lysosomal disorders including Niemann-Pick types A and B, these diseases are metabolically and genetically distinct. Niemann-Pick types A and B are caused by mutations in the SMPD1 gene, which encodes the enzyme sphingomyelinase, whereas NPC is caused by mutations in the NPC1 or NPC2 genes.

The incidence of NPC is approximately 1:120,000 to 1:150,000 live births. Age of onset is variable and ranges from the perinatal period to adulthood. Clinical presentation is also highly variable. Infants may present with or without liver disease (hepatosplenomegaly) and respiratory failure. Those without liver failure and pulmonary disease may present with hypotonia and developmental delay. Most individuals are diagnosed during childhood with symptoms including ataxia, vertical supranuclear gaze palsy, dystonia, progressive speech deterioration, and seizures resulting in death by the second or third decade of life. Adult onset NPC is associated with a slower progression and is characterized by neurologic and psychiatric problems.

NPC is inherited in an autosomal recessive manner, in which affected individuals carry 2 mutations in either the NPC1 or NPC2 gene. Most mutations are family specific, although there are 2 mutations in the NPC1 gene which are more common than others. The G992W mutation is common in the French Acadian population of Nova Scotia. The I1061T mutation is the most common mutation worldwide, and is seen in patients of Hispanic and Western European (United Kingdom and France) descent. Full gene sequencing and analysis for large deletions and duplications of the NPC1 and NPC2 genes detect less common disease-causing mutations.

The recommended first-tier test to screen for NPC is a biochemical test measuring cholesterol esterification coupled with filipin staining on a fibroblast specimen, NIEM/9313 Niemann-Pick Type C Detection, Fibroblasts. Molecular testing provides confirmation of a biochemical diagnosis or a basis for carrier testing of family members. Individuals with abnormal biochemical results are more likely to have 2 identifiable mutations by molecular testing.

An interpretive report will be provided.

An interpretative report will be provided.

The identification of a disease-causing mutation in an affected family member is necessary before predictive testing for other family members can be offered. If a familial mutation has not been previously identified, order NPCMS/89015 Niemann-Pick Type C, Full Gene Analysis.

Analysis is performed for the familial mutation(s) provided only. This assay does not rule out the presence of other mutations within this gene or within other genes that may be associated with Niemann-Pick type C.

Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Any error in the pedigree provided to us, including false-paternity, could lead to erroneous interpretation of results.

A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.

In addition to disease-related probes, the ligation-dependent probe amplification technique utilizes probes localized to other chromosomal regions as internal controls. In certain circumstances, these control probes may detect other diseases or conditions for which this test was not specifically intended. Results of the control probes are not normally reported. However, in cases where clinically relevant information is identified, the ordering physician will be informed of the result and provided with recommendations for any appropriate follow-up testing.

1. NP-C Guidelines Working Group, Wraith JE, Baumgartner MR, et al: Recommendations on the diagnosis and management of Niemann-Pick disease type C. Mol Genet Metab 2009 Sep-Oct;98(1-2):152-65

2. Park WD, O'Brien JF, Lundquist PA, et al: Identification of 58 novel mutations in Niemann-Pick disease type C: correlation with biochemical phenotype and importance of PTC1-like domains in NPC1. Hum Mutat 2003 Oct;22(4):313-325

3. Vanier MT: Niemann-Pick disease type C. Orphanet J Rare Dis. 2010 Jun 3;5:16

DNA sequence analysis is used to test for the presence of the specific mutation(s) in the NPC1 or NPC2 gene that were previously identified in an affected family member. Gene dosage analysis by multiplex ligation-dependent probe amplification is used to test for the presence of familial large deletions and duplications within these genes. (Unpublished Mayo method)

Thursday; 10 a.m.

81479- Unlisted molecular pathology procedure

81265 - Comparative analysis using Short Tandem Repeat {STRI markers; patient and comparative specimen (eg. Pretransplant recipient and donor germline testing, posttransplant non-hematopoietic recipient germline [eg, buccal swab or other germline tissue sample! and donor testing. twin zygosity testing, or maternal cell contamination of fetal cells) (if appropriate)

Amniotic Fluid Culture for Genetic Testing

88235-Tissue culture for amniotic fluid (if appropriate)

88240-Cryopreservation (if appropriate)

Fibroblast Culture for Genetic Testing

88233-Tissue culture, skin or solid tissue biopsy (if appropriate)

88240-Cryopreservation (if appropriate)