家族性低βリポタンパク血症1(ホモ接合体)

BACKGROUND: While low levels of LDL-cholesterol can be atheroprotective, homozygous Class I familial hypobetalipoproteinemia (Ho-Class I FHBL) and heterozygous Class I FHBL (He-Class I FHBL) due to APOB variants (i.e., heterozygous FHBL1 (HeFHBL1)) have serious complications due to genetic defects in the chylomicron/VLDL secretion pathway. However, Ho-Class I FHBL with milder phenotypes and HeFHBL1 are often underdiagnosed due to overlapping lipid profiles with other forms of hypobetalipoproteinemia. OBJECTIVE: Additional screening markers are warranted. METHODS: We established a prospective HBL cohort and performed detailed genotype-phenotype analyses to identify biomarkers associated with Class I FHBL. For further exploration, we systematically reviewed cases with Class I FHBL. RESULTS: In our lipid genome cohort (n = 440), whole-exome sequencing of 18 consecutive cases of HBL (LDL-C <30 mg/dL) identified 7 novel pathogenic variants in 7 cases of Class I FHBL. Genotype-phenotype analyses revealed that plasma vitamin K1 is the strongest independent predictor of Class I FHBL. The vitamin K1 levels in HeFHBL1 were significantly reduced by approximately 50% compared to controls, reflecting the half-normal lipoprotein secretion. Systematic review analyses (n = 472) revealed that vitamin K1 is the only fat-soluble vitamin that is significantly decreased not only in Ho-Class I FHBL but also in HeFHBL1. CONCLUSION: Plasma vitamin K1 may serve as a sensitive screening marker of fat malabsorption, facilitating the genetic diagnosis of Class I FHBL, enabling early management of its complications, such as fat malabsorption, fat-soluble vitamin deficiency, potential vitamin K deficiency, and steatotic liver disease.

Although genetic factors strongly influence lipid metabolism, genetic dyslipidemias refer to specific monogenic defects that significantly alter the function of proteins involved in lipid metabolism. Familial hypercholesterolemia results from mutations in the genes coding for LDL-receptor, apolipoprotein B100 (apoB100), PCSK9, or LDLRAP1. The rare homozygous form is severe, with extravascular lipid deposits at an early age and a high incidence of coronary events in childhood, in the absence of early diagnosis. The heterozygous form is more frequent and characterized by elevated plasma LDL-cholesterol levels (>190mg/dL in adults) and a very high risk of premature coronary artery disease (usually before the age of 50years). Familial chylomicronemia syndrome (FCS) is a major form of genetic hypertriglyceridemia caused by mutations in genes encoding lipoprotein lipase or one of its cofactors (apoC-II, apoA-V, GPIHBP1, or LMF1). Patients with FCS exhibit markedly elevated plasma triglyceride levels (>10mmol/L) and are at high risk for acute pancreatitis. Congenital familial partial lipodystrophy and glycogen storage diseases are two other forms of genetic hypertriglyceridemia. In addition, other rare genetic dyslipidemias have been described in humans, including familial dysbetalipoproteinemia, abetalipoproteinemia, familial hypobetalipoproteinemia, familial combined hypolipidemia, sitosterolemia, and hypoalphalipoproteinemias.

Background: The long-term clinical and laboratory results of a 33-year follow-up of a Greek family with abetalipoproteinemia (ABL) are described. Case Report: The patients (two brothers and their sister, aged 57, 49, and 62 years, respectively) are still alive, being under close surveillance. In two of the three patients, diarrhea appeared in early infancy, while in the third, it appeared during adolescence. CNS symptomatology worsened after the second decade of life. At the same time, night blindness appeared in the advanced stages of the disease, resulting in almost complete loss of vision in one of the male patients and severe impairment in the other. The diagnosis was based on the clinical picture, ophthalmological findings, serum lipid estimations, and presence of peripheral acanthocytosis. All patients exhibited typical serum lipidemic profile, ophthalmological findings, and acanthocytes in the peripheral blood. During the follow-up period, strict dietary modifications were applied, including the substitution of fat with medium-chain triglycerides (MCT oil). After 33 years since the initial diagnosis, all patients are alive without any sign of liver dysfunction despite continuous use of MCT oil. However, symptoms from the central nervous system and vision impairment worsened. Conclusion: The course of these patients suggests that the application of a modified diet, including MCT oil, along with close surveillance, could prolong the survival of patients without significant side effects from the liver.

An acellular dermal matrix is a biological graft composed of several components present in the dermis such as collagen fibers, elastin, fibronectin, and hyaluronic acid that serve as support for cellular repopulation that will gradually become vascularized. This provides mechanical resistance and improves suture retention. With this article we aim to present 2 cases, and our technique, in which a rupture of the distal triceps tendon occurred, patients presented late due to usual insurance authorization delays, and then required delayed surgical repair by means of dermal acellular matrix grafting in order to bridge the substantial gap due to tricep proximal retraction. The first case report describes a 55-year-old male with abetalipoproteinemia who suffered an unclear injury to his right triceps tendon and apparently an olecranon bursitis and/or tricep tendonitis. Surgical intervention involved exploring the triceps tendon, revealing degenerative tissue and a detached muscle belly that was unrepairable, necessitating immediate reconstruction with a dermal allograft. The poor quality of the triceps tendon, weakened by cortisone injections, precluded primary repair, highlighting the rationale for graft reconstruction. The second case concerns a 54-year-old male, a gym owner and amateur bodybuilder, who suffered a fracture of the lateral epicondyle with avulsion of the distal triceps following a motorcycle accident. The patient underwent surgery with end-to-end suturing of the tendon and augmentation of the suture using acellular dermal matrix. The successful use of a dermal allograft in surgical reconstruction presents a promising solution in cases with insufficient tendon quality.