A Rare Coincidence of Sitosterolemia and Familial Mediterranean Fever Identified by Whole Exome Sequencing

Children with Severe Hypercholesterolemia Caused by a Pathogenic Mutation in ABCG5

We herein present a case series of hypercholesterolemia caused by a pathogenic mutation in the ATP-binding cassette sub-family G member 5 (ABCG5). Three unrelated infantile patients who were breastfed and had extremely elevated low-density lipoprotein (LDL) cholesterol levels were referred to our hospital. Their LDL cholesterol levels decreased significantly after weaning. Panel sequencing revealed a pathogenic mutation in ABCG5 in each patient. An 8-year-old girl was also referred due to suspected familial hypercholesterolemia. Panel sequencing revealed a pathogenic mutation in ABCG5. A cholesterol-reduced diet alone significantly reduced the LDL cholesterol levels. Moreover, the administration of ezetimibe was found to be beneficial.

Pediatric patients with familially inherited sitosterolemia: Two case reports

Background

Sitosterolemia is a rare recessive genetic abnormality of hyperlipidemia; it is characterized by increased levels and accumulation of sitosterol in the plasma and local tissues.

Case descriptions

The study subjects were two siblings (brother and sister) who had sitosterolemia with systemic multiple xanthomas as the main manifestation. The main clinical manifestations were hypercholesterolemia, premature atherosclerosis, arrhythmia, systemic multiple xanthomas, etc. After genetic testing, it was found that the patients had a compound heterozygous mutation of c.1324+1de1G in exon 7 and exon 9 of chromosome 2p21 of the adenosine triphosphate binding cassette transporter G family member 5(ABCG5) gene; the mutation at c.904+1G>A was of maternal origin, and the mutation at c. 1324+1de1G was of paternal origin. The compound heterozygous mutation of these two genes led to a metabolic disorder of plant sterols in vivo.

Conclusion

Sitosterolemia is an autosomal recessive disease that could be effectively controlled after dietary control and oral lipid-lowering therapy with Ezetimibe. Xanthomas, which affects function and appearance, could be surgically removed, and primary wound healing could be achieved.

Association of familial Mediterranean fever and epicardial adipose tissue: A systematic review and meta‐analysis

Background and Aim

Some studies reported a positive link between familial Mediterranean fever (FMF) and epicardial adipose tissue. Our meta‐analysis aimed to evaluate whether there is a significant association between FMF and increased epicardial adipose tissue thickness.

Methods

We searched the following databases: PUBMED, WOS, OVID, SCOPUS, and EMBASE. Inclusion criteria were any original articles that reported epicardial adipose tissue in FMF patients with no age restriction, excluding reviews, case reports, editorials, animal studies, and non‐English studies. Thirty eligible studies were screened full text but only five studies were suitable. We used RevMan software (5.4) for the meta‐analysis.

Results

The total number of patients included in the meta‐analysis in the FMF patients group is 256 (mean age = 24.3), and the total number in the control group is 188 (mean age = 24.98). The pooled analysis between FMF patients and controls was [mean difference = 0.82 (95% CI = 0.25–1.39), p‐value = 0.005]. We observed heterogeneity that was not solved by random effects (p > 0.00001). We performed leave one out test by removing the Kozan et al. study, and the heterogeneity was solved (p = 0.07), and the results were (MD = 0.98, 95% CI = 0.52–1.43, p‐value < 0.0001).

Conclusion

FMF patients are at increased risk of developing epicardial adipose tissue compared to controls. More multicenter studies with higher sample sizes are needed to support our results.

Acute Coronary Syndrome Developed in a 17-year-old Boy with Sitosterolemia Comorbid with Takayasu Arteritis: A Rare Case Report and Review of the Literature

A 17-year-old boy with acute coronary syndrome was admitted to our hospital. He had xanthomas over his elbow and Achilles tendon and a high level of low-density lipoprotein cholesterol; therefore, his initial diagnosis was familial hypercholesterolemia. However, a genetic analysis revealed a compound heterozygous mutation in the ABCG5 gene with a high serum level of sitosterol, leading to the diagnosis of sitosterolemia. After lipid-lowering treatment, percutaneous coronary intervention was performed. Furthermore, a persistently high C-reactive protein level and images of large arteries led to a diagnosis of Takayasu arteritis. To our knowledge, this is the first case of sitosterolemia complicated by Takayasu arteritis.

Clinical, genetic profile and therapy evaluation of 55 children and 5 adults with sitosterolemia

BACKGROUND

Sitosterolemia is a rare autosomal recessive disease characterized by phytosterol accumulation in the blood and tissues. However, the detailed clinical and genetic spectra are lacking.

OBJECTIVE

To describe and compare the clinical, biochemical, genetic, therapeutic, and follow-up characteristics of 55 pediatric and five adult sitosterolemia patients.

METHODS

Clinical, genetic and therapeutic data from 60 patients at Xinhua Hospital from January 2016 to June 2021 were retrospectively collected.

RESULTS

Pediatric patients' manifestations included xanthomas(93%), hematological disorders(30%), arthralgia(24%), splenomegaly(11%), atherosclerosis(10%). Adult patients had symptoms such as atherosclerosis(5/5), xanthomas(4/5), hematological disorders(3/5), arthralgia(3/5), splenomegaly(3/5). Elevated total cholesterol(TC) and low-density lipoprotein cholesterol(LDL-C) were observed in 96% patients (pediatric 98%, adult 3/4), and phytosterol levels in 100% patients. The age of onset was also negatively correlated with blood TC (P < 0.0001, r = -0.5548) and LDL-C (P = 0.0001, r = -0.4859) levels. Targeted treatments resulted in symptomatic remission(pediatric 96%, adult 4/5), and significantly decreased lipid and phytosterol levels(all P<0.05). In the dietary-therapy cohort(n=34), blood lipid levels decreased(all P<0.05). In the 13 pediatric patients from the dietary-therapy cohort who switched from dietary to combination therapy with ezetimibe, dietary therapy decreased TC and LDL-C levels by 54% and 52%, and ezetimibe further decreased them by 18% and 20%, respectively. Further, we identified 15 novel ABCG5/ABCG8 variants.

CONCLUSIONS

This study expands the clinical and genetic spectra of sitosterolemia. The low-phytosterol diet is the cornerstone of sitosterolemia treatment. Ezetimibe can further decrease blood lipid levels and increase daily dietary phytosterol tolerance.

Diagnosis and Management of Sitosterolemia 2021

Sitosterolemia is an inherited metabolic disorder characterized by increased levels of plant sterols, such as sitosterol. This disease is caused by loss-of-function genetic mutations in ATP-binding cassette (ABC) subfamily G member 5 or member 8 ( ABCG5 or ABCG8 , respectively), both of which play important roles in selective excretion of plant sterols from the liver and intestine, leading to failure to prevent absorption of food plant sterols. This disorder has been considered to be extremely rare. However, accumulated clinical data as well as genetics suggest the possibility of a much higher prevalence. Its clinical manifestations resemble those observed in patients with familial hypercholesterolemia (FH), including tendon xanthomas, hyper LDL-cholesterolemia, and premature coronary atherosclerosis. We provide an overview of this recessive genetic disease, diagnostic as well as therapeutic tips, and the latest diagnostic criteria in Japan.

Beneficial effect of ezetimibe-atorvastatin combination therapy in patients with a mutation in ABCG5 or ABCG8 gene

Background

Use of ezetimibe on top of statin therapy has been shown to be effective to reduce LDL cholesterol level in hypercholesterolemic patients. However, little is known regarding the individual variety of the effectiveness of ezetimibe. We hypothesized that hypercholesterolemic patients with a mutation in ABCG5 or ABCG8 gene exhibit better response to ezetimibe than those without, based on the fact that ezetimibe is hyper-effective for in patients with sitosterolemia caused by ABCG5 or ABCG8 genetic mutations.

Methods

Electronical medical record were reviewed in a total of 321 hypercholesterolemic patients (baseline LDL cholesterol = 192 ± 46 mg/dl) prescribed ezetimibe 10 mg daily on top of atorvastatin 10 mg daily who had undergone genetic analysis of ABCG5 or ABCG8 gene in our institute since 2006 to 2017. Pathogenicity of the variants were determined using standard variant filtering schema, including minor allele frequency, in silico annotation tools. Patients were divided into 2 groups based on the presence of ABCG5 or ABCG8 mutation. We compared the percent reduction of LDL cholesterol as well as the achieved LDL cholesterol levels between these 2 groups.

Results

We found 26 (8%) individuals who exhibit deleterious mutations in ABCG5 or ABCG8 gene. Baseline characteristics under the atorvastatin 10 mg therapy were comparable in age, gender, and LDL cholesterol level between 2 groups. Under these conditions, percent reduction of LDL cholesterol in mutation positive group was significantly larger than that of mutation negative group (28 ± 16% vs. 39 ± 21%, p < 0.05). As a result, the achieved LDL cholesterol level in mutation positive group was significantly lower than that of mutation negative group (87 ± 29 mg/dl vs. 72 ± 26% mg/dl, p < 0.05).

Conclusion

These results suggest that ezetimibe-atorvastatin combination therapy might be more beneficial in hypercholesterolemic patients with a mutation in ABCG5 or ABCG8 gene.

Clinical features and genetic analysis of childhood sitosterolemia: Two case reports and literature review

RATIONALE

Sitosterolemia is a rare autosomal recessive disorder of dyslipidemia due to mutations of genes ABCG5 and ABCG8, leading to highly elevated plasma levels of plant sterols and expanded body pools of cholesterol.

PATIENT CONCERNS

We present a 9-year-old and a 7-year-old Chinese boy with hypercholesterolemia and xanthomas of sitosterolemia due to ABCG5 gene mutations. We also make a literature review of another 30 sitosterolemic children cases that have been reported with virulence ABCG5 gene mutations.

DIAGNOSIS

We took peripheral blood samples from 2 patients and their parents to conduct genetic analysis by next-generation sequencing (NGS) technologies.

INTERVENTIONS

The 2 patients received dietary modifications without pharmaceuticals treatment.

OUTCOMES

A c.1166G>A (Arg389His) homozygosis mutation in exon 9 was observed in case 1, whereas a c.751C>T (Gln251*) homozygosis mutation in exon 6 was found in case 2. Literature review found another 30 pediatric cases with sitosterolemia due to ABCG5 gene mutation. The lipid profile was normalized and xanthomas got smaller with combined therapy of a combined low-cholesterol and low-phytosterols diet.

LESSONS

These suggested that in patients (especially Asian patients) with multiple xanthomas, severe hypercholesterolemia, or elevated low-density lipoprotein-cholesterol, sitosterolemia should be considered in the differential diagnosis. Early diagnosis is important, and restriction of both cholesterol and phytosterols diet should suggested for these patients.

Screening of common genetic variants in the APOB gene related to familial hypercholesterolemia in a Saudi population: A case-control study

Familial hypercholesterolemia (FH) is a monogenic dominant inherited disorder of lipid metabolism characterized by elevated low-density lipoprotein levels, and is mainly attributable to mutations in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proportein convertase subtilisin/kexin type 9 (PCSK9) genes. Next-generation and exome sequencing studies have primarily involved genome-wide association analyses, and meta-analyses and next-generation studies examined a few single-nucleotide polymorphisms (rs151009667 and Val2095Glu) in the ApoB gene. The present study was conducted to investigate the association of APOB and patients with FH in a Saudi population.We genotyped 100 patients with FH and 100 controls for 2 polymorphisms in APOB using polymerase chain reaction-restriction fragment length polymorphism, followed by 3% agarose gel electrophoresis. The strength of the association between the genotype and allele frequencies with the risk of developing FH was evaluated. Clinical details and genotype analysis results were recorded.For the rs151009667 polymorphism, 18% of the CT genotypes were observed only in patients with FH. There was a positive association between CT and CC (odds ratio [OR] 45.07 [95% conflict of interest (CI), 2.67-759.1]; P = .0001) and between T and C (OR 87.8 [95% CI, 5.34-144.2]; P < .0001). However, no Val2095Glu mutations were found in patients with FH or controls. There was also no correlation between clinical characteristics and the rs151009667 polymorphism.In conclusion, we confirmed the association between the rs151009667 polymorphism and FH in a Saudi population. The Val2095Glu novel variant did not appear in either patients with FH or controls. Similar studies should be performed in different ethnic populations to rule out the role of this polymorphism in FH.

Sitosterolemia, Hypercholesterolemia, and Coronary Artery Disease

Sitosterolemia is a rare inherited disease characterized by increased levels of plant sterols, such as sitosterol. The cause of this disease is ATP-binding cassette (ABC) subfamily G member 5 or member 8 (ABCG5 or ABCG8, respectively) gene mutations. Recent advances in genetics have revealed that the prevalence of subjects with deleterious mutations in ABCG5 and/or ABCG8 genes could be more than 1 in ~200,000 individuals among the general population. Furthermore, accumulated evidence, including infantile cases exhibiting progression/regression of systemic xanthomas associated with LDL cholesterol levels, have shown that the elevation of LDL cholesterol seems to be the major cause of development of atherosclerosis and not the elevation of sitosterol. Regarding therapies, LDL apheresis, as well as proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, could be useful for sitosterolemia, in addition to ezetimibe and/or colestimide. In this study, we provide the current understanding and future perspectives of sitosterolemia, which is currently considered an extremely rare disorder but is expected to be much more prevalent in clinical settings.

Oral Fat Tolerance Test for Sitosterolemia and Familial Hypercholesterolemia: A Study Protocol

AIM

Sitosterolemia is an extremely rare, autosomal recessive disease characterized by high plasma cholesterols and plant sterols because of increased absorption of dietary cholesterols and sterols from the intestine, and decreased excretion from biliary tract. Previous study indicated that sitosterolemic patients might be vulnerable to post-prandial hyperlipidemia, including high remnant-like lipoprotein particles (RLP) level. Here we evaluate whether a loading dietary fat increases a post-prandial RLP cholesterol level in sitosterolemic patients compared to heterozygous familial hypercholesterolemic patients (FH).

METHODS

We recruit total of 20 patients: 5 patients with homozygous sitosterolemia, 5 patients with heterozygous sitosterolemia, and 10 patients with heterozygous FH as controls from May 2015 to March 2018 at Kanazawa University Hospital, Japan. All patients receive Oral Fat Tolerance Test (OFTT) cream (50 g/body surface area square meter, orally only once, and the cream includes 34% of fat, 74 mg of cholesterol, and rich in palmitic and oleic acids. The primary endpoint is the change of a RLP cholesterol level after OFTT cream loading between sitosterolemia and FH. We measure them at baseline, and 2, 4, and 6 hours after the oral fat loading.

RESULTS

This is the first study to evaluate whether sitosterolemia patients have a higher post-prandial RLP cholesterol level compared to heterozygous FH patients.

CONCLUSION

The result may become an additional evidence to restrict dietary cholesterols for sitosterolemia. This study is registered at University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN ID: UMIN000020330).

Post-prandial Remnant Lipoprotein Metabolism in Sitosterolemia

AIM

We aimed to clarify post-prandial accumulation of remnant-like particles (RLP) in patients with sitosterolemia.

METHODS

Oral fat tolerance test cream (Jomo Shokuhin, Takasaki, Japan) 50 g was given per body surface area (m²); blood sampling was performed at 2 h intervals up to 6 h. Plasma lipoprotein fractions and RLP fractions were determined in four sitosterolemic subjects with double mutations in ATP-binding cassette (ABC) sub-family G member 5 or member 8 (ABCG5 or ABCG8) gene (mean age=18 yr, median low-density lipoprotein cholesterol [LDL-C]=154 mg/dL), six heterozygous carriers (mean age=31 yr, median LDL-C=105 mg/dL), and five subjects with heterozygous familial hypercholesterolemia (FH, mean age=32 yr, median LDL-C=221 mg/dL). The incremental area under curve (iAUC) of lipids, including LDL-C, apolipoprotein B-48 (apoB48), RLP cholesterol (RLP-C), and RLP triglyceride (RLP-TG) were evaluated.

RESULTS

After oral fat load, there was no significant difference of the iAUC of LDL-C between sitosterolemia and heterozygous FH, whereas the iAUC of apoB48 was significantly larger in the sitosterolemic subjects compared with that of heterozygous FH (2.9 µg/mL×h vs. 1.3 µg/mL×h, p＜0.05). Under these conditions, the iAUCs of RLP-C and RLP-TG levels were significantly larger in the sitosterolemic subject compared with those of heterozygous FH (9.5 mg/dL×h vs. 5.7 mg/dL×h, p＜0.05; 149 mg/dL×h vs. 40 mg/dL×h, p＜0.05, respectively), whereas those of heterozygous carriers were comparable with those with heterozygous FH.

CONCLUSIONS

Post-prandial lipoprotein metabolism in sitosterolemia appeared to be impaired, leading to their elevation in serum sterol levels. (UMIN Clinical Trials Registry number, UMIN000020330).

Carotid intima media thickness in a girl with sitosterolemia carrying a homozygous mutation in the ABCG5 gene

BACKGROUND

Sitosterolemia is a rare lipid metabolism disorder that involves storage of plant sterols. This disease is associated with atherosclerosis, but detailed vascular endothelial assessment is difficult.

CASE PRESENTATION

We report a 5-year-old girl with sitosterolemia who presented with xanthomas at 23 months of age. Her total cholesterol was 868 mg/dL, and her plasma sitosterol level was 9.48 mg/dL. Direct sequencing detected a homozygous mutation in gene ABCG5 (p.Arg389His). Echocardiographic examination revealed that the carotid artery intima media thickness (cIMT) was 0.4 mm with heterogenous hyperechogenicity inside the arterial wall. She was treated using dietary therapy and ezetimibe, which effectively lowered her sitosterol levels. After 3 years of treatment, her cIMT was stable in diameter and arterial wall echogenicity had improved.

CONCLUSIONS

Sitosterolemia is a unique disorder in which it is difficult to avoid premature atherosclerosis because of high sitosterol levels. cIMT measurement with arterial wall assessment may improve management.

Clinical Perspectives of Genetic Analyses on Dyslipidemia and Coronary Artery Disease

We have learned that low-density lipoprotein (LDL) cholesterol is the cause of atherosclerosis from various aspects, including a single case with familial hypercholesterolemia, other cases with different types of Mendelian dyslipidemias, large-scale randomized controlled trials using LDL cholesterol lowering therapies, and Mendelian randomization studies using common as well as rare variants associated with LDL cholesterol levels. There is no doubt that determinations of genotypes in lipid-associated genes have contributed not only to the genetic diagnosis for Mendelian dyslipidemias but also to the discoveries of novel therapeutic targets. Furthermore, recent studies have shown that such genetic information could provide useful clues for the risk prediction as well as risk stratification in general and in particular population. We provide the current understanding of genetic analyses relating to plasma lipids and coronary artery disease.