Frequency of the cholesteryl ester storage disease common LIPA E8SJM mutation (c.894G>A) in various racial and ethnic groups

Authors


  • Potential conflict of interest: R.J.D. is a consultant for and owns stock options of Synageva BioPharma, the company developing enzyme replacement therapy for LAL deficiency.

  • Supported in part by the National Center for Advancing Translational Sciences (NCATS), National Institutes of Health (NIH), through grants KL2TR000069 (S.A.S.) and UL1TR000067 (I.P.).

Address reprint requests to: Robert J. Desnick, Ph.D., M.D., Dean for Genetic and Genomic Medicine, Professor and Chairman Emeritus, Department of Genetics and Genomic Sciences, Box 1498, Icahn School of Medicine at Mount Sinai, Fifth Avenue at 100th Street, New York, NY, 10029. E–mail: robert.desnick@mssm.edu fax: 212-360-1809

Abstract

Cholesteryl ester storage disease (CESD) and Wolman disease are autosomal recessive later-onset and severe infantile disorders, respectively, which result from the deficient activity of lysosomal acid lipase (LAL). LAL is encoded by LIPA (10q23.31) and the most common mutation associated with CESD is an exon 8 splice junction mutation (c.894G>A; E8SJM), which expresses only ∼3%-5% of normally spliced LAL. However, the frequency of c.894G>A is unknown in most populations. To estimate the prevalence of CESD in different populations, the frequencies of the c.894G>A mutation were determined in 10,000 LIPA alleles from healthy African-American, Asian, Caucasian, Hispanic, and Ashkenazi Jewish individuals from the greater New York metropolitan area and 6,578 LIPA alleles from African-American, Caucasian, and Hispanic subjects enrolled in the Dallas Heart Study. The combined c.894G>A allele frequencies from the two cohorts ranged from 0.0005 (Asian) to 0.0017 (Caucasian and Hispanic), which translated to carrier frequencies of 1 in 1,000 to ∼1 in 300, respectively. No African-American heterozygotes were detected. Additionally, by surveying the available literature, c.894G>A was estimated to account for 60% (95% confidence interval [CI]: 51%-69%) of reported mutations among multiethnic CESD patients. Using this estimate, the predicted prevalence of CESD in the Caucasian and Hispanic populations is ∼0.8 per 100,000 (∼1 in 130,000; 95% CI: ∼1 in 90,000 to 1 in 170,000). Conclusion: These data indicate that CESD may be underdiagnosed in the general Caucasian and Hispanic populations, which is important since clinical trials of enzyme replacement therapy for LAL deficiency are currently being developed. Moreover, future studies on CESD prevalence in African and Asian populations may require full-gene LIPA sequencing to determine heterozygote frequencies, since c.894G>A is not common in these racial groups. (HEPATOLOGY 2013;53:958–965)

Abbreviations
AJ

Ashkenazi Jewish

CESD

Cholesteryl Ester Storage Disease

CHD

coronary heart disease

CI

confidence interval

DHS

Dallas Heart Study

E8SJM

exon 8 splice junction mutation

IRB

institutional review board

LAL

lysosomal acid lipase

LIPA

lipase A

NAFLD

nonalcoholic fatty liver disease

NASH

nonalcoholic steatohepatitis

The deficient activity of lysosomal acid lipase (LAL), which hydrolyzes cholesteryl esters and triglycerides, results in either cholesteryl ester storage disease (CESD) or the more severe Wolman disease.[1, 2] LAL is encoded by the LIPA gene (10q23.31)[3] and homozygous and compound heterozygous LIPA mutations that result in little or no LAL activity cause Wolman disease, a severe infantile-onset disorder characterized biochemically by the massive storage of cholesteryl esters and triglycerides primarily in the liver, intestines, and adrenals leading to hepatosplenomegaly, adrenal calcification, vomiting, diarrhea, anemia, failure to thrive, and death typically before 1 year of age.[4] In contrast, LIPA mutations with residual LAL activity result in CESD, which is characterized by hepatosteatosis, hepatomegaly, splenomegaly, dyslipidemia, accelerated atherosclerosis, and premature demise.[1, 2, 5, 6]

Although over 40 LIPA mutations have been identified in patients with Wolman disease and CESD, the most common LIPA mutation is the c.894G>A exon 8 splice junction mutation (i.e., E8SJM; p.delS275_Q298; rs116928232). This mutation results in a transcript with an in-frame deletion of exon 8 that encodes a mutant enzyme with no residual LAL activity; however, the splicing defect also allows ∼3%-5% normally spliced LAL with enzyme activity.[5, 7] Since the c.894G>A mutation results in residual LAL activity, it has only been found among patients with CESD and not Wolman disease.[8, 10] In contrast, neighboring exon/intron 8 splice junction mutations, c.892C>T (E8SJM-3) and c.894+1G>A (E8SJM+1), are rare null alleles that have been detected in patients with Wolman disease. Interestingly, c.894G>A heterozygotes recently were found to have elevated total cholesterol compared to normolipidemic Caucasian controls, which may also impart an increased risk of coronary heart disease (CHD).[11] The association of LIPA as a susceptibility gene for CHD has been strengthened further by recent genome-wide association studies.[12]

The frequency of CESD in different populations is unknown, but it is generally thought that the disease is often unrecognized. For example, it can be misdiagnosed in patients with hepatomegaly following a liver biopsy as nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), or cryptogenic fatty liver disease.[15] To estimate the prevalence of CESD, a previous study investigated the frequency of the c.894G>A CESD mutation in the German population and identified an allele frequency of 0.0025 (1 in 202 carrier frequency).[16] Among the reported CESD patients who had undergone LIPA mutation analyses, c.894G>A previously was estimated to account for ∼50% of all CESD alleles.[16] As such, with this assumption, the identified 0.0025 c.894G>A allele frequency predicted a CESD prevalence of ∼2.4 per 100,000 in the German population.

Since no LIPA c.894G>A allele frequencies exist for other racial or ethnic groups, including the African-American, Asian, or Hispanic populations, efforts were directed to determine the c.894G>A frequencies in individuals from five major racial and ethnic groups from both the New York metropolitan area and the Dallas Heart Study. The frequency of the c.894G>A mutation in various populations and its prevalence among CESD patients can be used to estimate the prevalence of CESD, which may encourage hepatologists, lipidologists, pathologists, geneticists, and metabolic physicians to identify CESD patients, since clinical trials of enzyme replacement therapy for LAL deficiency are under way and may provide safe and effective therapy.

Materials and Methods

c.894G>A Prevalence in CESD

The prevalence of the c.894G>A mutation among unrelated multiethnic CESD patients was estimated by searching the available literature and CESD case reports. The PubMed database (NCBI) was searched using the keywords (CESD OR Cholesteryl Ester Storage Disease) AND (mutation) from 1966 to September 2012. Studies were considered for inclusion if LIPA mutation status was reported for unique patient(s) with clinically confirmed CESD. Only a single affected patient was included in the LIPA mutation prevalence calculation when reports included multiple affected family members with the same mutations. Additionally, the Human Gene Mutation Database (HGMD) Professional (http://www.biobase-international.com/product/hgmd) was interrogated for CESD-causing LIPA mutations.

Study Population

New York Metropolitan Area

Peripheral blood samples from healthy donors who indicated their racial/ethnic background and gave informed consent for the use of their DNA for research were obtained from the New York Blood Center with Institutional Review Board (IRB) approval.[17, 18] In addition, blood samples were obtained with informed consent from unrelated, healthy 100% Ashkenazi Jewish (AJ) individuals from the greater New York metropolitan area as previously defined.[19, 20] All personal identifiers were removed and isolated DNA samples were tested anonymously. Genomic DNA was isolated using the Puregene DNA Purification kit (Qiagen, Valencia, CA) according to the manufacturer's instructions. For this study, 1,000 individuals each from five different populations (African-American, Asian, Caucasian, Hispanic, and AJ) were subjected to c.894G>A genotyping.

Dallas Heart Study

The Dallas Heart Study (DHS) is a multiethnic population-based probability sample of Dallas County residents (ages 18-85), weighted to include ∼50% of African-American subjects. Sampling design and recruitment procedures have been described in detail.[21] The study was transformed from a cross-sectional study to a longitudinal study in 2007 (DHS-2) when all prior DHS participants were invited to the clinic for a repeat evaluation. Race or ethnic identity was self-reported according to a list of categories used in the United States census. A total of 3,401 individuals submitted blood samples and provided written consent for genetic analyses. For this study, 1,720 African-American, 1,089 Caucasian, and 480 Hispanic participants from the DHS-2 cohort were subjected to c.894G>A genotyping. The study was approved by the IRB of the University of Texas Southwestern Medical Center at Dallas.

Genotyping

LIPA c.894G>A genotyping was performed using custom-designed TaqMan allelic discrimination assays (Applied Biosystems, Carlsbad, CA) as described in the Supporting Data. Selected mutation carriers were confirmed by bidirectional sequencing with independent M13-tagged LIPA amplification primers (forward: 5′-TGCTTTGAAGGGCAAAATAC-3′; reverse: 5′-TTTCTATTTGGAAAGGGTTTGC-3′) and analyzed using Mutation Surveyor software v. 3.30 (SoftGenetics).

CESD Prevalence

Prevalence of CESD was calculated using identified c.894G>A allele frequencies and adjusting for the prevalence of c.894G>A among CESD patients, as reported.[16]

Results

Prevalence of the c.894G>A Mutation in CESD

To estimate the prevalence of the c.894G>A mutation among unrelated multiethnic patients with CESD, a literature survey was conducted that revealed that c.894G>A accounted for 60% (95% confidence interval [CI]: 51%-69%) of reported multiethnic CESD mutations (n = 55 patients) (Table 1). These results are consistent with the previous c.894G>A estimate of ∼50% among CESD patients.[16]

Table 1. LIPA Mutations Among 55 Unrelated Patients With Cholesteryl Ester Storage Disease (CESD)
MutationFrequency (n)EthnicityReference
  1. NR: not reported.
Missense/Nonsense Mutations   
c.193C>T (p.R65X)0.018 (2)FrenchRedonnet-Vernhet et al., 1997 (33)
  CzechLohse et al., 2000 (34)
c.254A>G (p.Q85R)0.009 (1)BrazilianPagani et al., 1998 (9)
c.260G>T (p.G87V)0.009 (1)SicilianPagani et al., 1996 (10)
c.283T>A (p.W95R)0.009 (1)CzechElleder et al., 1999 (35)
c.356A>G (p.N119S)0.009 (1)AustralianHooper et al., 2008 (36)
c.386A>G (p.H129R)0.009 (1)SwissRies et al., 1998 (37)
c.386A>C (p.H129P)0.018 (2)AustrianGasche et al., 1997 (38)
  AustrianRies et al., 1998 (37)
c.419G>A (p.W140X)0.009 (1)CroatianFasano et al., 2012 (39)
c.435T>A (p.D145E)0.009 (1)CzechElleder et al., 1999 (35)
c.599T>C (p.L200P)0.009 (1)NRMaslen et al., 1995 (40)
c.605C>T (p.P202L)0.009 (1)ItalianPagani et al., 1996 (10)
c.652C>T (p.R218X)0.009 (1)ItalianPisciotta et al., 2009 (41)
c.796G>T (p.G266X)0.009 (1)Polish-GermanAslanidis et al., 1996 (5)
c.863C>T (p.T288I)0.018 (2)ItalianPagani et al., 1998 (9)
c.866C>G (p.S289C)0.009 (1)African-AmericanAnderson et al., 1999 (32)
c.881T>C (p.L294S)0.009 (1)ItalianPagani et al., 1996 (10)
c.883C>T (p.H295Y)0.045 (5)SicilianPagani et al., 1994 (42)
  ItalianRedonnet-Vernhet et al., 1997 (33)
  ItalianFasano et al., 2012 (39)
c.1024G>A (p.G342R)0.018 (2)African-AmericanAnderson et al., 1999 (32)
  GreekFasano et al., 2012 (39)
c.1070T>C (p.L357P)0.009 (1)Canadian-NorwegianSeedorf et al., 1995 (43)
Splicing Mutations   
c.676-2A>G0.009 (1)ItalianPagani et al., 1996 (10)
c.894G>A0.600 (65)Polish-GermanKlima et al., 1993 (7)
  NRMaslen et al., 1995 (40)
  Canadian-NorwegianSeedorf et al., 1995 (43)
  GermanAmeis et al., 1995 (44)
  SpanishMuntoni et al., 1995 (8)
  SicilianPagani et al., 1996 (10)
  Polish-GermanAslanidis et al., 1996 (5)
  Italian, FrenchRedonnet-Vernhet et al., 1997 (33)
  AustrianGasche et al., 1997 (38)
  BrazilianPagani et al., 1998 (9)
  AustrianRies et al., 1998 (37)
  BrazilianDu et al., 1998 (45)
  CzechElleder et al., 2000 (46)
  NRAnderson et al., 1999 (32)
  Germanvom Dahl et al., 1999 (47)
  CzechElleder et al., 2000 (46)
  Irish, CzechLohse et al., 2000 (34)
  GermanRassoul et al., 2001 (48)
  GermanDrebber et al., 2005 (49)
  NRTadiboyina et al., 2005 (50)
  AustralianHooper et al., 2008 (36)
  ItalianPisciotta et al., 2009 (41)
  Italian, Greek, CroatianFasano et al., 2012 (39)
Small Insertions/Deletions   
c.397_398delTC (p.V134Ffs*4)0.009 (1)NRAnderson et al., 1999 (32)
c.594insT (p.A199Cfs*13)0.009 (1)NRTadiboyina et al., 2005 (50)
c.635delC (p.P212Lfs*5)0.009 (1)CzechElleder et al., 2000 (46)
c.684delT (p.F228Lfs*13)0.009 (1)IrishLohse et al., 2000 (34)
c.967_968delAG (p.S323Lfs*44)0.009 (1)GermanAmeis et al., 1995 (44)
c.980delC (p.T327Nfs*4)0.009 (1)NRAnderson et al., 1999 (32)
c.1028delG (p.G343Vfs*15)0.009 (1)CzechLohse et al., 2000 (34)
Gross Deletions   
intron 1 to exon 40.009 (1)SwissRies et al., 1998 (37)
Complex Rearrangements   
c.229-33_c.230dup, c.232_245del (p.G77fs*5)0.009 (1)ItalianPisciotta et al., 2009 (41)
    
Undetermined Mutations0.064 (7)Polish-GermanKlima et al., 1993 (7)
  ItalianPagani et al., 1996 (10)
  NRAnderson et al., 1999 (32)
  CzechElleder et al., 1999 (35)

c.894G>A Allele and Carrier Frequencies

The identified c.894G>A allele and carrier frequencies are summarized in Table 2 and a representative sequence chromatogram of a confirmed heterozygote is illustrated in Fig. 1. The c.894G>A allele frequencies from the New York metropolitan area cohort ranged from 0.0005 (Asian) to 0.0015 (Caucasian and Hispanic), which translated to carrier frequencies of 1 in 1,000 to 1 in 333, respectively. The c.894G>A allele frequencies from the DHS cohort ranged from 0.0018 (Caucasian) to 0.0021 (Hispanic), which translated to carrier frequencies of 1 in 272 to 1 in 240, respectively. No African-American carriers were detected in either cohort. Additionally, the Caucasian and Hispanic c.894G>A frequency data from the New York and Dallas cohorts were combined, which resulted in similar allele frequencies of 0.0017 and carrier frequencies of 1 in 298 and 1 in 296, respectively. Of note, with a c.894G>A carrier frequency of ∼1 in 300 and a detectability of only 0.60, Bayesian analysis indicates that the residual risk of being a CESD carrier after negative c.894G>A carrier screening in the Caucasian and Hispanic populations would be ∼1 in 500.

Table 2. LIPA c.894G>A and Predicted Cholesteryl Ester Storage Disease (CESD) Frequencies
PopulationCarriers/ ScreeneesAllele Frequency (95% CI)Carrier FrequencyPredicted c.894G>A HomozygotesPredicted Affecteda (95% CI)
  1. CI: confidence interval.
  2. aPresuming c.894G>A accounts for ∼60% (95% CI: 51%-69%) of CESD mutations (see Table 1).
  3. bData previously reported (16).
  4. cCombined New York, Dallas, and Germany (16) Caucasian data.
Caucasian3/1,0000.00150.0030 (1 in 333)∼0.2 in 100,000∼0.6 in 100,000; 1 in 160,000
(New York) (0.000-0.003)  (1 in 114,898 to 1 in 212,553)
      
Caucasian4/1,0890.00180.0037 (1 in 272)∼0.3 in 100,000∼0.9 in 100,000; 1 in 106,733
(Dallas) (0.000-0.004)  (1 in 76,646 to 1 in 141,790)
      
Caucasian7/2,0890.00170.0034 (1 in 298)∼0.3 in 100,000∼0.8 in 100,000; 1 in 128,246
(New York + Dallas) (0.000-0.003)  (1 in 92,095 to 1 in 170,369)
      
Caucasian10/2,0230.00250.0049 (1 in 202)∼0.6 in 100,000∼1.7 in 100,000; 1 in 58,932
(Germany)b (0.001-0.004)  (1 in 42,320 to 1 in 78,289)
      
Combined Caucasianc17/4,1120.00210.0041 (1 in 242)∼0.4 in 100,000∼1.2 in 100,000; 1 in 84,250
  (0.001-0.003)  (1 in 60,501 to 1 in 111,922)
      
Hispanic3/1,0000.00150.0030 (1 in 333)∼0.2 in 100,000∼0.6 in 100,000; 1 in 160,000
(New York) (0.000-0.003)  (1 in 114,898 to 1 in 212,553)
      
Hispanic2/4800.00210.0042 (1 in 240)∼0.4 in 100,000∼1.2 in 100,000; 1 in 82,944
(Dallas) (0.000-0.005)  (1 in 59,563 to 1 in 110,187)
      
Hispanic5/1,4800.00170.0034 (1 in 296)∼0.3 in 100,000∼0.8 in 100,000; 1 in 126,167
(New York + Dallas) (0.000-0.003)  (1 in 90,602 to 1 in 167,607)
      
Ashkenazi Jewish2/1,0000.00100.0020 (1 in 500)∼0.1 in 100,000∼0.3 in 100,000; 1 in 360,000
  (0.000-0.002)  (1 in 258,520 to 1 in 478,243)
      
Asian1/1,0000.00050.0010 (1 in 1,000)∼0.1 in 400,000∼0.1 in 100,000; 1 in 1,440,000
  (0.000-0.001)  (1 in 1,034,080 to 1 in 1,912,974)
      
African-American0/1,000
(New York)     
      
African-American0/1,720
(Dallas)     
Figure 1.

Illustration of LIPA exon 8 and DNA sequence chromatogram from a representative heterozygous c.894G>A carrier. Mutation position is highlighted by an asterisk.

Predicted Prevalence of CESD

The predicted prevalence of affected individuals with CESD in the different populations, assuming Hardy-Weinberg equilibrium, is also summarized in Table 2. CESD prevalence was calculated using the identified c.894G>A allele frequencies and adjusting for the prevalence of c.894G>A among CESD patients. Assuming that the c.894G>A mutation accounts for 60% (95% CI: 51%-69%) of known multiethnic CESD mutations, the predicted prevalence of CESD in the Caucasian population of the greater New York metropolitan area is ∼0.6 per 100,000 (1 in 160,000; 95% CI: 1 in 114,898 to 1 in 212,553) and ∼0.9 per 100,000 among Caucasians from the DHS (1 in 106,733; 95% CI: 1 in 76,646 to 1 in 141,790). When combined, the prevalence in the general Caucasian population was determined to be ∼0.8 per 100,000 (1 in 128,246; 95% CI: 1 in 92,095 to 1 in 170,369). For the Hispanic population, CESD prevalence was estimated at ∼0.6 in 100,000 and ∼1.2 in 100,000 in the New York and Dallas cohorts, respectively, and ∼0.8 in 100,000 (1 in 126,167; 95% CI: 1 in 90,602 to 1 in 167,607) in the combined Hispanic population.

Discussion

The lack of reported frequency data for the LIPA c.894G>A mutation prompted our genotyping study using 5,000 DNA samples from a multiracial and multiethnic, healthy adult population and 3,289 additional multiracial and multiethnic adult samples from the Dallas Heart Study. To the best of our knowledge, this is the first report detailing the c.894G>A allele and carrier frequencies in the African-American, Asian, Caucasian, Hispanic, and AJ populations. Importantly, these data allow for predictions of CESD prevalence in these populations, which indicate that CESD may be underdiagnosed in the general population.

Recently, a phase I/II clinical trial of enzyme replacement therapy was conducted with recombinant human LAL in patients with CESD.[22] Intravenous administration of enzyme ranging from 0.35-3.0 mg/kg proved safe and well-tolerated and resulted in decreased levels of hepatic transaminases in all patients with evidence of tissue lipid mobilization. These encouraging results suggest the future possibility of a treatment for CESD patients. As such, it is important that hepatologists, lipidologists, and pathologists are made aware of the clinical presentation of this underrecognized disease and its frequency to identify potential patients. In particular, hepatologists and pathologists can order the appropriate histologic liver biopsy stains (e.g., immunostaining with a lysosomal membrane protein to document lysosomal cholesteryl ester and triglyceride storage).[15] Additionally, lipidologists can identify some patients with dyslipidemia for LAL enzyme or LIPA gene screening prior to liver biopsy.[23] These efforts should detect and biochemically and/or molecularly confirm CESD patients who are candidates for enzyme replacement therapy. Thus, the frequencies of the common c.894G>A mutation in different populations can determine those racial and ethnic groups in which the mutation is present or very rare to absent.

Previously, a single c.894G>A screening study reported a 1 in 202 heterozygote frequency in the German population.[16] Importantly, our survey of reported CESD patient genotypes indicated that the LIPA c.894G>A mutation accounted for ∼60% (95% CI: 51%-69%) of multiethnic CESD alleles. However, the majority of ascertained CESD patients were of European ancestry. Consequently, the reported c.894G>A allele frequency (0.0025) translates to a predicted CESD prevalence of ∼1.7 in 100,000 (1 in 58,932; 95% CI: 1 in 42,320 to 1 in 78,289) for the German population.

Genotyping the c.894G>A mutation in individuals of different racial and ethnic groups from the New York metropolitan area and from the DHS indicated that c.894G>A frequencies vary between populations and are highest among populations of European ancestry. Interestingly, the c.894G>A frequencies were equally high among Hispanics. The identified carrier frequencies for the combined Caucasian and Hispanic populations were both ∼1 in 300, which translated to a predicted CESD prevalence of ∼0.8 per 100,000 (∼1 in 130,000) using the c.894G>A prevalence among affected multiethnic individuals (60%). Importantly, these data suggest that CESD may be underdiagnosed in the general North American population, particularly among Caucasians and Hispanics, as the predicted frequency of affected individuals markedly exceeds the relative paucity of cases reported in the literature. Additionally, selected populations of central European ancestry may have an even higher prevalence of CESD based on the c.894G>A frequency reported for the German population and the number of CESD case reports involving European patients. For example, when combining the New York and Dallas cohorts with the German data, the combined Caucasian carrier frequency increased to 1 in 242, which translated to a predicted CESD prevalence of ∼1.2 in 100,000 (1 in 84,250; 95% CI: 1 in 60,501 to 1 in 111,922).

Other lysosomal storage disorders with prevalence estimates similar to that for CESD in the Caucasian and Hispanic populations include metachromatic leukodystrophy (1 in 92,000), Fabry disease (1 in 117,000), mucopolysaccharidosis types I (1 in 88,000), II (1 in 136,000), III-A (1 in 114,000), and IV (1 in 169,000), and Pompe disease (1 in 146,000).[26] Given the estimated population of Caucasians and Hispanics currently living in the United States,[31] the predicted prevalence of CESD translates to potentially over 3,000 affected Caucasian and Hispanic individuals in the U.S. at the time of this writing.

Although c.894G>A was rare in the Asian and African-American populations, it is not currently known if this allele is the major CESD-causing mutation in these populations as it is for populations of European decent. This is evidenced by a previously reported African-American CESD patient who did not carry c.894G>A, unlike the majority of reported CESD cases, but instead was a compound heterozygote for two different LIPA missense mutations (p.S289C and p.G342R).[32] Similarly, the recent NHLBI Exome Sequencing Project (http://evs.gs.washington.edu/EVS/) also did not identify any c.894G>A heterozygotes in 4,406 African-American chromosomes. Consequently, future studies on the prevalence of CESD in African and Asian populations may require full-gene LIPA sequencing to determine CESD heterozygote frequencies, since c.894G>A is not common in these racial groups.

In addition to multiethnic population studies on LIPA allele frequencies, future focused studies are warranted that interrogate the c.894G>A and other LIPA mutations among patients with evidence of hepatomegaly and/or steatosis. Since this was not the primary aim of the reported study, limited data were available to assess the relevant phenotypes of identified c.894G>A carriers. However, available data from four patients from the DHS suggest that c.894G>A heterozygotes may have elevated hepatic triglyceride content indicative of steatosis (data not shown), which is supported by the recent identification of increased total cholesterol levels in c.894G>A carriers compared to noncarriers.[11] Future LIPA sequencing studies directed at patients with NAFLD, NASH, and/or cryptogenic fatty liver disease will undoubtedly further refine the role of CESD in fatty liver disease.

Acknowledgments

The genotyping testing methodology and reagents used in this study were generously provided by Synageva BioPharma (Lexington, MA). The authors thank Dr. Helen H. Hobbs (Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX) for use of critical resources funded by her grants RO1DK090066 and PO1 HL20948.

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