Familial Cholesterolemia - Case Study Example

Etiology

Familial hypercholesterolemia (FH) is primary dyslipidemia that affects the manner in which cholesterol is processed in the body. Therefore, persons with this condition have higher chances of suffering heart diseases as well as a higher risk of experiencing heart attack at an early age. The disorder results from gene mutations that encode the low-density lipoprotein receptors. Since this is a co-dominant disorder, an individual with a pair of mutant LDL receptor alleles is more vulnerable compared to those with a single mutant allele. FH is thus caused by defects on chromosome 19, which weaken the body; thus making it unable to excrete the LDL cholesterol from the bloodstream (Talmud et al., 2013). In effect, this causes a rise of LDL levels within the blood system. As a result, a patients arteries will start to narrow from atherosclerosis from a tender age. Futema et al. (2015) state that parents pass on these gene mutations to their children in a manner referred to as autosomal dominant, which implies that for an individual to inherit the condition, they have to acquire a copy of the abnormal gene from one of their parents. In most occasions, people with this disease often have one normal gene and one affected gene. However, there are insignificant chances of an individual to inherit an altered copy from both parents although such an incidence may increase the severity of the condition.

Mechanism

Familial hypercholesterolemia (FH) is qualified by elevated serum LDL cholesterol levels because of increased deposition of cholesterol in tissues, leading to enhanced atherosclerosis and increased risk of early coronary heart attack. The FH infection results from the LDL degradation through the receptor pathway, hepatic defects and gene mutation (Beliard et al., 2014). This autosomal dominant disorder thus causes gene dosage effect. An FH recessive forms because of LDLRAP1's loss-of-function mutations. The LDLRAP1 serves to encode a protein that assists in internalization of the LDL receptor (Versmissen et al., 2016). Recently, scientists added the PCSK9 protein to the existing gene database. A gain of function mutations of this protein increases the levels of plasma LDL-C that causes accelerated atherosclerosis and premature heart disease. Contrarily, loss of function mutation leads to low LDL-C concentrations, thus protecting an individual from early coronary heart disease. Therefore, these features make PCSK9 to be a target for the medical interventions with the aim of reducing serum LDL cholesterol.

Prevalence

The familial hypercholesterolemia is quite common in some populations. In fact, some studies suggest that FH is more prevalent in some communities than statistical estimates. A factor attributed to the founder effect. However, FH prevalence still exists even in the absence of the founder effect. Raal et al. (2015) estimate the total population of FH patients at between 14 to 34 million across the globe. However, available evidence shows that only 50% of the FH diagnosed patients are privileged to be receiving appropriate treatment intervention.

Diagnostic Techniques

There are three distinct techniques for Familial Hypercholesterolemia diagnosis. They include Simon Broome, Dutch Lipid Clinic Network, and MEDPED diagnostic criteria.

Simon Broome Diagnostic Criteria

(Austin, M. A., Hutter, C. M., Zimmern, R. L., & Humphries, S. E. (2004). Genetic causes of monogenic heterozygous familial hypercholesterolemia: A Huge Prevalence Review. American Journal of Epidemiology, 160(5), 407-420.)

Dutch Lipid Clinic Network Diagnostic Criteria

(Austin, M. A., Hutter, C. M., Zimmern, R. L., & Humphries, S. E. (2004). Genetic causes of monogenic heterozygous familial hypercholesterolemia: A Huge Prevalence Review. American Journal of Epidemiology, 160(5), 407-420.)

MEDPED Diagnostic Criteria

(Austin, M. A., Hutter, C. M., Zimmern, R. L., & Humphries, S. E. (2004). Genetic causes of monogenic heterozygous familial hypercholesterolemia: A Huge Prevalence Review. American Journal of Epidemiology, 160(5), 407-420.)

Prognosis

The FH outcome mainly relies on proper intake of prescribed medications as well as appropriate lifestyle modifications as they can significantly reduce the risk of heart disease. Scientific evidence indicates that exercise, changes in diet and proper medication can dramatically reduce the level of cholesterol among those with a mild form of FH disorder thus considerably delaying the occurrence of coronary heart attack. Moreover, FH increases the likelihood of the risk of early heart attack with evidence showing that untreated females are likely to develop symptoms of heart disease at the early fifties while males in early forties. Homozygous FH patients (those who inherit the defective gene from both parents) are at a higher risk of experiencing an early coronary heart attack before 30 years of age. In such cases, the outcome may be poor.

Further Symptoms

High levels of cholesterol in the body can lead to stroke, hardening and narrowing of the arteries (atherosclerosis), heart attacks and angina (chest pain) from heart disease. Patients suffering from this condition are likely to experience xanthomas; fatty skin deposits on the elbows, buttocks, knees, and tendons. The other likely symptoms are corneal arcus and xanthelasmas; cholesterol deposits around cornea and eyelids respectively (Talmud et al., 2013). A peripheral vascular disease is also a common symptom that is likely to make such patients experience pain while walking. It is also worth noting that individuals from FH families often have a distinct pattern where they exude higher levels of cholesterol at different ages that ultimately result in heart disease or heart attack.

Nutritional and Non-nutritional Treatment

The most recommended dietary treatment for FH patients is a diet low in cholesterol and fat. Healthcare professionals often advise FH patients to minimize intake of trans fat and saturated fats. Shamburek et al. (2016) advise that this group of people should increase their consumption of monounsaturated and polyunsaturated fats. These can be obtained through including tree nuts into the diet, consumption of fortified foods with sterols or stanols and consumption of fewer than two meals rich in fat. Talmud et al. (2013) also suggest that consumption of fatty marine fishb high-fiber content foods, soy proteins and marine driven omega-3 obtained from fatty-acid supplements are quite beneficial to this group of patients.

On the other hand, an FH patient should undertake regular exercise as one of the non-nutritional treatment options. For a considerable period, researchers have carried out extensive studies to determine how physical activity influences serum lipid levels in the body. According to Singaraja et al. (2014), the meta-analysis of various published data on the topic demonstrates that regular aerobic exercise positively influences lipid levels through increasing HDL cholesterol levels. Contrarily, empirical evidence indicates that physical inactivity posits critical adverse implications on the body's lipid metabolism. Therefore, since dietary approaches often lower the triglyceride, LDL cholesterol, and cholesterol levels while exercise, on the other hand, increases the level of HDL cholesterol while reducing triglyceride levels, Talmud et al. (2013) suggest that these two approaches should be combined as nutritional and non-nutritional FH treatment intervention measures.

References

Austin, M. A., Hutter, C. M., Zimmern, R. L., & Humphries, S. E. (2004). Genetic causes of monogenic heterozygous familial hypercholesterolemia: A Huge Prevalence Review. American journal of epidemiology, 160(5), 407-420.

Beliard, S., Carreau, V., Carrie, A., Giral, P., Duchene, E., Farnier, M., ... & Moulin, P. (2014). Improvement in LDL-cholesterol levels of patients with familial hypercholesterolemia: Can we do better? Analysis of results obtained during the past two decades in 1669 French subjects. Atherosclerosis, 234(1), 136-141.

Futema, M., Shah, S., Cooper, J. A., Li, K., Whittall, R. A., Sharifi, M., ... & Defesche, J. (2015). Refinement of variant selection for the LDL cholesterol genetic risk score in the diagnosis of the polygenic form of clinical familial hypercholesterolemia and replication in samples from 6 countries. Clinical Chemistry, 61(1), 231-238.

Nordestgaard, B. G., & Benn, M. (2017). Genetic testing for familial hypercholesterolaemia is essential in individuals with high LDL cholesterol: Who does it in the world?.

Raal, F. J., Stein, E. A., Dufour, R., Turner, T., Civeira, F., Burgess, L., ... & Hovingh, G. K. (2015). PCSK9 inhibition with evolocumab (AMG 145) in heterozygous familial hypercholesterolaemia (RUTHERFORD-2): A randomised, double-blind, placebo-controlled trial. The Lancet, 385(9965), 331-340.

Santos, R. D., Gidding, S. S., Hegele, R. A., Cuchel, M. A., Barter, P. J., Watts, G. F., ... & Folco, E. (2016). Defining severe familial hypercholesterolaemia and the implications for clinical management: A consensus statement from the International Atherosclerosis Society Severe Familial Hypercholesterolemia Panel. The Lancet Diabetes & Endocrinology, 4(10), 850-861.

Shamburek, R. D., Bakker-Arkema, R., Auerbach, B. J., Krause, B. R., Homan, R., Amar, M. J., ... & Remaley, A. T. (2016). Familial lecithin: cholesterol acyltransferase deficiency: First-in-human treatment with enzyme replacement. Journal of Clinical Lipidology, 10(2), 356-367.

Singaraja, R. R., Tietjen, I., Hovingh, G. K., Franchini, P. L., Radomski, C., Wong, K., ... & Hubbard, B. (2014). Identification of four novel genes contributing to familial elevated plasma HDL cholesterol in humans. Journal of Lipid Research, 55(8), 1693-1701.

Talmud, P. J., Shah, S., Whittall, R., Futema, M., Howard, P., Cooper, J. A., ... & Neil, H. A. W. (2013). Use of low-density lipoprotein cholesterol gene score to distinguish patients with polygenic and monogenic familial hypercholesterolaemia: a case-control study. The Lancet, 381(9874), 1293-1301.

Versmissen, J., Vongpromek, R., Yahya, R., Net, J. B., Varkvan der Zee, L., BlommesteijnTouw, J., ... & Dahlback, B. (2016). Familial hypercholesterolaemia: cholesterol efflux and coronary disease. European Journal of Clinical Investigation, 46(7), 643-650.