Background: Sitosterolemia is a rare autosomal recessive disorder characterized by diverse clinical manifestations ranging from asymptomatic cases to the development of xanthomas, hypercholesterolemia, premature atherosclerosis, or even sudden death during childhood. It results from homozygous or compound heterozygous pathogenic variants in the ABCG5 or ABCG8 genes. Prompt detection and intervention are essential to managing this condition and preventing severe outcomes. Methods: This study aims to retrospectively analyze the phenotype, genotype, treatment, and outcomes of 14 children—seven boys and seven girls—all of Vietnamese origin, diagnosed with sitosterolemia at the Vietnam National Children’s Hospital between March 2015 and July 2024. Results: The median ages at disease onset and diagnosis were 5.7 years (range: 1.5–17.9) and 7.2 years (range: 1.7–17.9), respectively. Xanthomas were observed in 85.7% of patients (12/14), arthralgia in 14.3% (2/14), and anemia in 7.1% (1/14), with no cases of thrombocytopenia. At diagnosis, all patients exhibited elevated total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), with considerably higher levels in patients with xanthomas compared to those without. Mutations in the ABCG5 gene were identified in 71.4% (10/14) of the patients, while 28.6% (4/14) had mutations in the ABCG8 gene. Fourteen variants were detected, nine in ABCG5 and five in ABCG8, with five variants reported for the first time in sitosterolemia patients. Initial management for all patients involved dietary modifications. After three months, 10 patients with persistently elevated TC and LDL-C received ezetimibe or cholestyramine treatment. Among the eight patients who continued treatment for over three months, the median TC and LDL-C concentrations decreased by 54.9% and 67.3%, respectively. Conclusions: Among Vietnamese patients with sitosterolemia, variants in the ABCG5 gene were more prevalent than those in the ABCG8 gene. Patients showed a positive response to ezetimibe or cholestyramine treatment. Genetic testing is essential for establishing a diagnosis of sitosterolemia and guiding accurate management strategies.

Background and Objectives: Hyperornithinemia–hyperammonemia–homocitrullinuria syndrome (HHH; OMIM 238970) is one of the rare urea cycle disorders. Ornithine carrier 1 deficiency causes HHH syndrome, characterized by failure of mitochondrial ornithine uptake, hyperammonemia, and accumulation of ornithine and lysine in the cytoplasm. The initial presentation and time of diagnosis in HHH highly varies. Genetic analysis is critical for diagnosis. Materials and Methods: This study encompassed retrospective and prospective analyses of four unrelated Vietnamese children diagnosed with HHH syndrome. Results: The age of diagnosis ranged from 10 days to 46 months. All four cases demonstrated hyperornithinemia and prolonged prothrombin time. Three out of four cases presented with hyperammonemia, elevated transaminases, and uraciluria. No homocitrulline was detected in the urine. Only one case depicted oroticaciduria. Genetic analyses revealed three pathogenic variants in the SLC25A15 gene, with the c.535C>T (p.Arg179*) variant common in Vietnamese patients. The c.562_564del (p.Phe188del) and c.408del (p.Met137Cysfs*10) variants were detected in one case. The latter variant has yet to be reported in the literature on HHH patients. After intervention with a protein-restricted diet, ammonia-reducing therapy, and L-carnitine supplementation, hyperammonemia was not observed, and liver enzyme levels returned to normal. Conclusions: Our results highlighted the clinical and biochemical heterogeneity of HHH syndrome and posed that HHH syndrome should be considered when individuals have hyperammonemia, elevated transaminase, and decreased prothrombin time.

October 17, 2024 Dear Prof. Dr. Rizzo and Dr. Oshiro, Prof. Dr. Rizzo: Editor-in-Chief of the Endocrinology section. Dr. Oshiro: Guest Editor of the “Advances in Clinical Diabetes, Obesity, and Metabolic Diseases” special Issue. I would like to submitt the manuscript entitled “Hyperornithinemia-Hyperammonemia-Homocitrullinuria Syndrome in Vietnamese Patients” by Khanh Ngoc Nguyen et al. to be considered for publication as an article in the “Advances in Clinical Diabetes, Obesity, and Metabolic Diseases” of the “Medicina” journal. This study included retrospective and prospective analyses of four unrelated Vietnamese children diagnosed with Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. HHH syndrome is one of the rarest urea cycle disorders and is characterized by failure of mitochondrial ornithine uptake, hyperammonemia, and accumulation of ornithine and lysine in the cytoplasm. Genetic analysis is key for diagnosis. In this study, we report the phenotype, genotype, treatment, and outcome of the four patients. To our best knowledge, this study is the first report of HHH patients in Vietnam. A diverse onset age and delayed diagnosis were observed. All four cases showed hyperornithinemia and prolonged prothrombin time. Three out of four cases presented with hyperammonemia, elevated transaminases, and uraciluria. No homocitrulline was detected in the urine. Genetic analyses identified three pathogenic variants in the SLC25A15 gene. The c.535C>T (p.Arg179*) variant is a common variant in Vietnamese patients. The c.562_564del (p.Phe188del) and c.408del (p.Met137Cysfs*10) variants were found in one case. The latter variant has yet been reported in the HHH patients in the literature. After intervention with a protein-restricted diet, ammonia-reducing therapy, and L-carnitine supplementation, no case had hyperammonemia and liver enzyme levels returned to normal range. Our results high-lighted clinical and biochemical heterogeneity of HHH syndrome and suggested that HHH syndrome should be considered when individuals present with hyperammonemia, elevated transaminase, and decreased prothrombin time. We believe these findings will be of interest to the readers of Medicina. We confirm that neither the manuscript nor any parts of its content are currently under consideration for publication with or published in another journal. All authors approved the final version of the manuscript and agree with its submission to Medicina. Thank you for your time and effort. We look forward to hearing from you regarding our submission. Yours sincerely, Chi Dung Vu (PhD., Assoc. Prof.) Center of Endocrinology, Metabolism, Genetic/Genomics and Molecular Therapy, Vietnam National Children’s Hospital, 18/879 La Thanh, Dong Da, Hanoi, Vietnam Email: dungvu@nch.gov.vn. Tel: +84-246-2747643