ESPE Abstracts

Familial hypobetalipoproteinemia (FHBL) is an autosomal codominantly inherited disorder of lipid metabolism characterized by <5th percentile plasma levels of LDL cholesterol or total apolipoprotein B (apoB). LDL cholesterol level is usually between 20-50 mg/dL. FHBL results from mutations in APOB, PCSK9 gene. Patients with homozygous APOB-related familial hypobetalipoproteinemia (APOB-FHBL) may have symptoms of fat malabsorption, steatorrhea, diarrhea, failure to thrive, deficiencies of fat-soluble vitamin, and neurologic dysfunction. They usually have hepatomegaly and hepatic steatosis. These patients may need a low-fat diet and supplementation of fat-soluble vitamins. Patients with heterozygous APOB-FHBL are usually asymptomatic with mild liver dysfunction and hepatic steatosis. They are often diagnosed incidentally due to low cholesterol levels and generally do not require special treatment or restriction of fat intake. A 14-year-old Korean boy was referred to our clinic due to his low level of low-density lipoprotein (LDL) cholesterol and elevation of aminotransferases. When he presented to our clinic, his height, weight and body mass index were 164 cm (-0.14 standard deviation score [SDS]), 56.9 kg (0.09 SDS), and 21.15 kg/m2 (0.13 SDS), respectively. He complained no specific symptom of hypobetalipoproteinemia, including growth retardation, steatorrhea, and neurologic dysfunction. His laboratory test showed low LDL cholesterol (25.5 mg/dL; reference value, 0-100 mg/dL), low apolipoprotein B (14 mg/dL; reference value, 66-133 mg/dL), and elevated aminotransferases (AST, 41 U/l [reference value, 0~34 U/L]; ALT, 69 U/l [reference value, 10~49 U/L]). Although he was not obese, abdominal computed tomography showed severe fatty liver and hepatosplenomegaly. There was no history of alcohol consumption, systemic infection and exposure to herbal medications or hepatotoxic chemicals, so he was diagnosed with nonalcoholic fatty liver disease. A multigene panel associated with hereditary dyslipidemia was conducted. A heterozygous mutation for p.Lys3846Ter (c.11536A>T) was identified in the APOB gene, which had not been reported in previous studies. That variation was classified as likely pathogenic variant according to ACMG guidelines. The same mutation was not detected in his parents, and his parents showed high or normal LDL cholesterol, and normal apolipoprotein B. Therefore, the patient was diagnosed with de novo heterozygous FHBL. He started oral vitamin E (alpha-tocopherol) 1,000 IU daily because of his low alpha-tocopherol (4.0 mg/L; reference value, 5.5-17.0 mg/dL) and he is being followed up regularly.