Assessment of plasma chitotriosidase activity, CCL18/PARC concentration and NP-C suspicion index in the diagnosis of Niemann-Pick disease type C: a prospective observational study.

BACKGROUND: Niemann-Pick disease type C (NP-C) is a rare, autosomal recessive neurodegenerative disease caused by mutations in either the NPC1 or NPC2 genes. The diagnosis of NP-C remains challenging due to the non-specific, heterogeneous nature of signs/symptoms. This study assessed the utility of plasma chitotriosidase (ChT) and Chemokine (C-C motif) ligand 18 (CCL18)/pulmonary and activation-regulated chemokine (PARC) in conjunction with the NP-C suspicion index (NP-C SI) for guiding confirmatory laboratory testing in patients with suspected NP-C. METHODS: In a prospective observational cohort study, incorporating a retrospective determination of NP-C SI scores, two different diagnostic approaches were applied in two separate groups of unrelated patients from 51 Spanish medical centers (n = 118 in both groups). From Jan 2010 to Apr 2012 (Period 1), patients with ≥2 clinical signs/symptoms of NP-C were considered 'suspected NP-C' cases, and NPC1/NPC2 sequencing, plasma chitotriosidase (ChT), CCL18/PARC and sphingomyelinase levels were assessed. Based on findings in Period 1, plasma ChT and CCL18/PARC, and NP-C SI prediction scores were determined in a second group of patients between May 2012 and Apr 2014 (Period 2), and NPC1 and NPC2 were sequenced only in those with elevated ChT and/or elevated CCL18/PARC and/or NP-C SI ≥70. Filipin staining and 7-ketocholesterol (7-KC) measurements were performed in all patients with NP-C gene mutations, where possible. RESULTS: In total across Periods 1 and 2, 10/236 (4%) patients had a confirmed diagnosis o NP-C based on gene sequencing (5/118 [4.2%] in each Period): all of these patients had two causal NPC1 mutations. Single mutant NPC1 alleles were detected in 8/236 (3%) patients, overall. Positive filipin staining results comprised three classical and five variant biochemical phenotypes. No NPC2 mutations were detected. All patients with NPC1 mutations had high ChT activity, high CCL18/PARC concentrations and/or NP-C SI scores ≥70. Plasma 7-KC was higher than control cut-off values in all patients with two NPC1 mutations, and in the majority of patients with single mutations. Family studies identified three further NP-C patients. CONCLUSION: This approach may be very useful for laboratories that do not have mass spectrometry facilities and therefore, they cannot use other NP-C biomarkers for diagnosis.

Impact of low-density lipoprotein receptor mutational class on carotid atherosclerosis in patients with familial hypercholesterolemia.

BACKGROUND AND OBJECTIVES: Defects in the low-density lipoprotein receptor (LDLR) gene cause familial hypercholesterolemia (FH), a highly atherogenic condition. The effect of different LDLR mutations on coronary heart disease (CHD) risk is insufficiently defined. We assessed carotid intima-media thickness (IMT), a surrogate marker of CHD, in relation to LDLR mutational class in FH. METHODS: In 436 Spanish FH patients (223 men and 213 women, age 44+/-14 years) with known LDLR mutations, alleles were classified by standard criteria as null (n=269), defective (n=162), or undetermined (n=5). LDLR defects were detected using a microarray (Lipochip) designed to uncover prevalent mutations in Spain and gene sequencing when no mutations were detected. Carotid IMT and plaque were assessed in FH patients and 268 healthy subjects. RESULTS: All carotid measurements were increased in FH patients versus controls (p<0.05), irrespective of genotype. After adjustment for gender and age, patients with null alleles compared with defective alleles had similar mean and maximum common carotid artery (CCA) IMT, but higher maximum IMT at any carotid segment, with median values (95% confidence interval) of 1.25 mm (1.19-1.31) and 1.11 mm (1.05-1.18), respectively. Multivariate analysis showed that null alleles were independently associated with maximum CCA-IMT (beta=0.09, p=0.033) with an impact similar to that of gender (beta=0.10, p=0.035). CONCLUSIONS: FH patients show advanced carotid atherosclerosis in relation to LDLR mutational class. The findings support the utility of genetic testing in FH beyond providing a secure diagnosis.

Frequency of low-density lipoprotein receptor gene mutations in patients with a clinical diagnosis of familial combined hyperlipidemia in a clinical setting.

OBJECTIVES: The purpose of this study was to determine the frequency of mutations in the low-density lipoprotein receptor (LDLR) and apolipoprotein B (APOB) genes in consecutive patients with a clinical diagnosis of familial combined hyperlipidemia (FCH) in a nonresearch setting. BACKGROUND: The lipid phenotype frequently overlaps in familial hypercholesterolemia (FH) and FCH. Detection of causative mutations in LDLR or APOB provides an unequivocal diagnosis of FH, but such genetic testing has not been systematically performed in FCH. METHODS: We used Lipochip (Progenika, Derio, Spain), a microarray that includes 203 causative mutations in LDLR and 4 APOB defects, to investigate 143 unrelated FCH patients. RESULTS: Mutations of LDLR were found in 28 patients (overall prevalence, 19.6%). No APOB defects were found. Compared with patients who had a normal LDLR gene, patients with mutations had lower waist circumference (p = 0.02); significantly (p < 0.005) higher total cholesterol, non-high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and apoB; nonsignificantly (p = 0.063) lower triglycerides; and a lower frequency of diabetes mellitus (22% vs. 0%, respectively; p = 0.002). Total cholesterol and apoB levels showed the best receiver-operator characteristics curves in the prediction of LDLR mutations, with areas under the curve (95% CI: of 0.750 (95% confidence interval [CI]: 0.647 to 0.853) and 0.744 (95% CI: 0.636 to 0.851), respectively. Total cholesterol of 335 mg/dl and apoB of 185 mg/dl were the best thresholds for diagnosis of LDLR mutations. CONCLUSIONS: Screening for LDLR defects is advisable for patients with a clinical diagnosis of FCH showing high total cholesterol or apoB levels. Diagnostic criteria for FH should not exclude patients whose personal and familial lipid values appear to fit the clinical criteria of FCH.

Femoral atherosclerosis in heterozygous familial hypercholesterolemia: influence of the genetic defect.

OBJECTIVE: The purpose of this study was to assess femoral atherosclerosis by ultrasound in patients with molecularly defined heterozygous familial hypercholesterolemia (FH) in comparison with matched control subjects and in relation to mutational class in the LDL receptor and apolipoprotein B (APOB) genes. METHODS AND RESULTS: Femoral intima-media thickness (IMT) and plaque were evaluated in 146 FH patients carrying null alleles (n=48), defective-receptor alleles (n=62), undetermined-function alleles (n=25), or APOB defects (n=11) and in 193 healthy subjects. Twenty-three patients had coronary heart disease (CHD). The frequency of both tendon xanthomas and CHD was approximately 2-fold higher and average LDL cholesterol was 30 mg/dL higher in null-allele genotype compared with receptor-defective mutations. All femoral measurements were increased in FH patients versus controls (P<0.001), and null-allele mutations showed higher age-, sex-, and LDL cholesterol-adjusted maximum IMT than receptor-defective or APOB defects (P for trend, 0.001). By multivariate analysis, independent associations of mean IMT, a measure of early atherosclerosis, were age, LDL cholesterol, sex, and systolic blood pressure. Age, null-allele genotype, sex, and smoking explained 42% of the variability of maximum IMT, a measure of advanced atherosclerosis. CONCLUSIONS: FH patients have increased femoral IMT in relation to mutational class. The findings support the usefulness of genetic testing in FH beyond securing the diagnosis.