Transient infantile hypertriglyceridemia is one of the diseases that should be considered in case of unexplained elevated liver enzymes, hypertriglyceridemia and hepatosteatosis. We report 2 siblings with novel homozygous variants in the GPD1 gene with transient infantile hypertriglyceridemia. Two siblings born from consanguineous marriage were referred due to hepatomegaly, elevated transaminases and fatty liver. After excluding other possible causes of fatty liver and elevated transaminase levels; whole-exome sequencing (WES) was performed on genomic DNA isolated from the peripheral blood samples of both patients. Whole exome sequencing revealed the identification of a novel homozygous variant, c.628 G > C:p.G210R, in GPD1. Our report underscores the importance of genome sequencing in diagnosing unexplained childhood fatty liver disease and/or elevated enzyme levels. In patients with transient infantile hypertriglyceridemia, investigation into novel homozygous variants in the GPD1 gene should be conducted using whole exome sequencing.

Transient infantile hypertriglyceridemia (TIH) is a syndrome of hypertriglyceridemia, fatty liver, and deranged liver functions with progression to fibrosis and cirrhosis. It is an autosomal recessive disorder caused by mutations in Glycerol-3-phosphate dehydrogenase 1 gene present on Chromosome 12q12-q13, and has been reported in Israeli Arab families with high consanguinity. TIH is suspected by high serum triglyceride levels and steatosis on liver biopsy; however, diagnosis is confirmed on clinical exome sequencing. We present two cases of TIH belonging to the indigenous Hindu, hilly population of Himachal Pradesh in North India with no history of either consanguinity or family history. The parents of both the cases were counselled regarding the disease and importance of growth and lipid level monitoring. Though TIH is an extremely rare entity, awareness about it is required as it is a contributor to non-alcoholic fatty liver disease (NAFLD) in children. Any child presenting with hepatomegaly and elevated fasting triglyceride levels should be further investigated for TIH.

Transient infantile hypertriglyceridemia (HTGTI) is caused by mutations in the glycerol-3-phosphate dehydrogenase 1 (GPD1) gene. HTGTI is characterized by hypertriglyceridemia, hepatomegaly, hepatic steatosis and fibrosis in infancy. Here, we reported first Turkish HTGTI patient with a novel mutation of GPD1, having hypertriglyceridemia, hepatomegaly, growth retardation and hepatic steatosis. He is the first case who needs transfusion until 6th month in GPD1. A 2-month-27-day-old boy, who had growth retardation, hepatomegaly and anemia suffered to our hospital with vomiting. Triglyceride level was 1603 mg/dL (n<150). Liver transaminases were elevated and hepatic steatosis was developed. He needed transfusion with erythrocyte suspension until 6th month. Etiology could not be elucidated by clinical and biochemical parameters. A novel homozygous c.936_940del (p.His312GlnfsTer24) variant was detected in the GPD1 gene by Clinical Exome Analysis. GPD1 deficiency should be investigated in the presence of unexplained hypertriglyceridemia and hepatic steatosis in children especially in infants.

Objective : Our study aims to summarize and analyze the clinical characteristics of transient infantile hypertriglyceridemia (HTGTI) and variants in the glycerol-3-phosphate dehydrogenase 1 (GPD1) gene and the effect of HTGTI on the protein structure of GPD1. Methods: Retrospective analysis, using the general data, symptoms, signs, and auxiliary examinations, was performed on patients with HTGTI, which were confirmed by genetic testing in our hospital and reported cases online. The clinical data were analyzed using statistical and bioinformatic approaches. Results: A total of 31 genetically confirmed HTGTI patients were collected from our hospital and cases reported in the literature. The clinical manifestations showed the median age of onset was 6.0 (1.9, 12.0) months. All the patients had normal psychiatric status, but 22.6% of them presented growth retardation and short stature, 93.5% had hepatomegaly, and 16.1% had splenomegaly. Just a few children were reported with jaundice, cholestasis, and obesity (3.2-6.5%). The laboratory investigations showed that 96.8% of them had hypertriglyceridemia (HTG) with a median level of 3.1 (2.1, 5.5) mmol/L, but only 30.0% had returned to normal during follow-up. In addition, 93.5% of patients had elevated alanine aminotransferase (ALT) with an average level of 92.1 ± 43.5 U/L, while 38.7% had hypercholesterolemia. Upon abdominal imaging, all patients presented fatty liver and liver steatosis, with 66.7% of patients showing hepatic fibrosis. Statistical differences in triglyceride (TG) level were observed in the ≤6 months group compared with the older groups and in the 13 months to 6 years group with >6 years group (H = 22.02, P < 0.05). The restricted cubic spline model showed that severe HTG decreased in the early stage of infants to the normal level; however, it rebounded again to a mild or moderate level after the following days. The genetic test revealed that the main variant types of the GPD1 gene were missense variants (51.6%), followed by splicing variants (35.5%) and nonsense variants (12.9%). Of patients, 87.1% had homozygous variants, with the most frequent loci being c.361-1G > C and c.895G > A. Conclusion: The common manifestations of HTGTI were HTG, hepatomegaly, elevated liver transaminases, and hepatic steatosis in early infancy. However, the recurrence of aberrant HTG may pose long-term detrimental effects on HTGTI patients.

1例随访1年余的3-磷酸甘油脱氢酶（GPD1）基因突变致婴儿期短暂性高甘油三酯血症（HTGTI）患儿并复习文献，发现HTGTI婴儿期起病为主，临床以肝大、脂肪肝、高脂血症、轻度转氨酶异常为特征。且有长期甚至延续至成年的肝脏脂肪代谢异常、肝酶升高以及生长发育问题，故长期干预及远期预后值得临床医生关注。.