A case of autosomal recessive hypercholesterolemia with a novel mutation in the LDLRAP1 gene

Background: Autosomal recessive hypercholesterolemia (ARH) is a rare monogenic disorder resulting from mutations of the LDLRAP1 gene, which leads to elevated LDL-C levels. Here, using whole exome sequencing (WES), we describe a 22-year-old Iranian female who carries a novel nonsense mutation in LDLRAP1. Methods: Genetic investigations were performed for the patient and her family. She showed LDL-C level of 720 mg/dL since the age of 11 years. At the age of 13 years old, aortic valve repair surgery was performed due to severe aortic valve stenosis (AVS). At the age of 17, along with prescription of rosuvastatin plus ezetimibe, coronary angiography displayed the presence of serious stenotic lesions of the coronary arteries and also aortic valve, making the patient eligible for coronary artery bypass grafting (CABG) and aortic valve replacement (AVR). Results: Genetic analysis showed the presence of a previously unreported homozygous LDLRAP1 gene variant, c.649G>T, generating a nonsense mutation at amino acid 217, shortening the ARH protein from 308 to 217 amino acid, which removes AP-2 binding domain of ARH, as an important part in LDL uptake.Conclusion: During a 10-year treatment, we observed a 74% reduction in LDL-C level. Despite the treatment with maximal dose of rosuvastatin plus ezetimibe, the results of coronary angiography demonstrated severe supravalvular aortic stenosis (SVAS) resulted in significant stenotic lesions of the coronary arteries and aortic valve. This highlights the importance of WES in early diagnosis of ARH, and it is proposed to prevent or at least delay the onset of the cardiovascular events.

An Iranian patient affected by autosomal recessive hypercholesterolemia due to a novel variant in the LDLRAP1 gene

Background: Autosomal recessive hypercholesterolemia (ARH) is a rare monogenic disorder resulting from mutations of the LDLRAP1 gene, which leads to elevated LDL-C levels. Here, using whole exome sequencing (WES), we describe a 22-year-old Iranian female who carries a novel nonsense mutation in LDLRAP1. Methods: Genetic investigations were performed for the patient and her family. She showed LDL-C level of 720 mg/dL since the age of 11 years. At the age of 13 years old, aortic valve repair surgery was performed due to severe aortic valve stenosis (AVS). At the age of 17, along with prescription of rosuvastatin plus ezetimibe, coronary angiography displayed the presence of serious stenotic lesions of the coronary arteries and also aortic valve, making the patient eligible for coronary artery bypass grafting (CABG) and aortic valve replacement (AVR).Results: Genetic analysis showed the presence of a previously unreported homozygous LDLRAP1 gene variant, c.649G>T, generating a nonsense mutation at amino acid 217, shortening the ARH protein from 308 to 217 amino acid, which removes AP-2 binding domain of ARH, as an important part in LDL uptake.Conclusion: During a 10-year treatment, we observed a 74% reduction in LDL-C level. Despite the treatment with maximal dose of rosuvastatin plus ezetimibe, the results of coronary angiography demonstrated severe supravalvular aortic stenosis (SVAS) resulted in significant stenotic lesions of the coronary arteries and aortic valve. This highlights the importance of WES in early diagnosis of ARH, and it is proposed to prevent or at least delay the onset of the cardiovascular events.

Homozygous autosomal recessive hypercholesterolaemia in a South Asian child presenting with multiple cutaneous xanthomata

Autosomal recessive hypercholesterolemia (ARH; OMIM #603813) is an extremely rare disorder of lipid metabolism caused by loss-of-function variants in the LDL receptor adapter protein 1 ( LDLRAP1) gene, which is characterized by severe hypercholesterolaemia and an increased risk of premature atherosclerotic cardiovascular disease. We report the case of an 11-year-old girl who presented with multiple painless yellowish papules around her elbows and knees of two-year duration. She had been reviewed by several general practitioners, with some of the papules having been excised, but without a specific diagnosis being made. The child was referred to a paediatric service for further evaluation and treatment of the cutaneous lesions, which appeared xanthomatous in nature. A lipid profile showed severe hypercholesterolaemia. Next generation sequencing analysis of a monogenic hypercholesterolaemia gene panel revealed homozygosity for a pathogenic frameshift mutation, c.71dupG, p.Gly25Argfs*9 in LDLRAP1. Her parents and brother, who were asymptomatic, were screened and found to be heterozygous carriers of the LDLRAP1 variant. There was no known consanguinity in the family. She was commenced on the HMG-CoA reductase inhibitor, atorvastatin, to good effect, with a ∼76% reduction in LDL-cholesterol at a dose of 50 mg per day. At six-month follow-up, there had been no obvious regression of the xanthomata, but importantly, no enlargement of, or the development of new papular lesions, have occurred. In summary, we report a child who presented with multiple cutaneous xanthomata and was confirmed to have ARH by the presence of a homozygous novel pathogenic frameshift variant in LDLRAP1.