Phenylketonuria Case Study Paper Example

Introduction

Phenylketonuria (PKU) is an autosomal recessive disease defined by deficient activity of the enzyme phenylalanine hydroxylase (PAH), which is needed to convert the essential amino acid phenylalanine (phe) to tyrosine (Macleod & Ney, 2010). As an inborn metabolism error, PKU manifest soon after childbirth and is characterized by highly deficient protein metabolism. For patients with PKU, ingesting a phe-rich diet triggers abnormal phenylalanine levels in the blood, brain and tissues. If unmanaged, phenylalanine accumulation results in significant detrimental effects including mental retardation and melanin dysfunction.

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By definition, phenylketonuria is understood as an accumulation of phenylketones, usually detectable in urine. PKU was first described as a source of mental retardation by Asbjorn Folling in 1934. While treating children suffering progressive mental retardation, the Norwegian scientist noticed urine irregularities characterized by high concentrations of phenyl pyruvic acid. The accumulating keto-acid was later understood as a metabolite of phenylalanine and in 1953, Horst Bickel's group working at the Birmingham Children's Hospital in the UK reported the effectiveness of a low-phe diet in reducing phe concentrations and improving behavior in a child with PKU (Macleod & Ney, 2010). Even though alternative methods are gaining ground, life-long nutritional management remains the most reliable option for people living with phenylketonuria. To ensure safe phe concentrations, phenylketonuria patients are limited to strictly controlled diets alongside regular intake of low-phe dietary supplements.

Phenylketonuria is an inherited disorder caused by mutations in the phenylalanine hydroxylase gene. Being autosomal recessive, the disorder is only inherited when both parents contribute the defective gene, resulting in an offspring with two alleles in their recessive form. As a standard, if both parents have PKU, the offspring will inevitably inherit the disorder. In some cases, the gene is passed on without associated health detriments resulting in a carrier of the defective genes. Although unaffected, bearing offspring with another carrier might result in PKU transference. If only one parent is a carrier of the defective genes, the offspring will not inherit PKU defects. In most cases, the disorder is transferred when both parents are unaware of the fact that they are carriers. Taking research into account, classic PKU is the most common and also most severe form of phenylketonuria. Unlike milder versions such as variant PKU and non-phenylketonuria hyperphenylalaninemia, classic PKU results in either absence or severe reduction in PAH activity.

Categorically, abnormality in the PAH genes found on chromosome 12 affects encoding of the phenylalanine hydroxylase enzyme. Dysfunction of PAH enzyme impairs major functions such as protein breakdown, and destabilizes both melanin and hormone production. Typically, phenylalanine hydroxylase serves as a catalyst in the conversion of phenylalanine into tyrosine. Both phenylalanine and tyrosine are useful amino acids and are an essential part of a healthy diet. Under normal conditions, the body constantly works to maintain optimum phe levels in the blood, usually about 1 mg/dl. After intake of phe-rich foods, amino acids are broken down and phenylalanine is released. This results in increased phe levels in the bloodstream. To prevent toxic phe buildup, the body eliminates phenylalanine in two productive ways; protein synthesis and metabolic conversion where phe is transformed into tyrosine. Although both serve important functions, protein synthesis accounts for only about 25% of phe management. The remaining part is handled by amino acid metabolism, usually in the liver or even the kidneys as well. The significantly large amounts of unmanaged phe in untreated PKU patients explains the detrimental effects that result.

In normal protein metabolism, phenylalanine is converted into tyrosine in a reduction reaction catalyzed by phenylalanine hydroxylase. In tyrosine form, the phenylalanine becomes more useful to the body. Typically, phe is converted into p-hydroxyphenylpyruvate, a conjugate base of 4-hydroxyphenylpyruvic acid, and eventually into forms of acetic acid that can be handle by the body. Contrarywise, in patients with PKU, the conversion of phe into tyrosine is either halted or impaired, depending on the severity of the condition. This results in ineffective conversion of phenylalanine into tyrosine, ultimately resulting in excessively high phe levels in the blood. The main part affected by toxic phenylalanine levels is the brain. This can be attributed to the phe-sensitivity of brain nerve cells. In PKU patients, unprocessed phenylalanine undergoes reduction in the absence of PAH, resulting in the formation of phenyl pyruvic acid. While circulating in the blood stream, phenyl pyruvic acid crosses the blood brain barrier and enters the cerebrospinal fluid. This explicates the relationship between PKU and mental retardation.

In a PKU patient, phe levels increase astronomically soon after birth. This necessitates regulation of phe intake and artificial compensation of low amino acid intake using low-phe formulas. Newborn screening has remained the preferred way of early PKU detection since the 1960s. Since then, dietary improvements and pharmaceutical treatments have emerged including the use of synthetic variations of tetrahydrobiopterin - the natural co-factor for PAH enzyme. Among the common pharmaceutical treatments is sapropterin dihydrochloride. Studies show that sapropterin dihydrochloride is well tolerated, lowers blood Phe, and improves Phe tolerance in approximately 25-50% of individuals with PKU (Lichter-Konecki & Vockley, 2019). As the probe on alternative medications continues, life-long nutritional management remains the most reliable option for people living with phenylketonuria.

According to Macleod et al (2010), the goal of nutritional management for those with PKU is to maintain plasma phe concentrations that support optimal growth, development, and mental functioning while providing a nutritionally complete diet. Although scientists have not yet fully agreed on optimum plasma phe concentrations for patients living with PKU, American and European doctors employ a range of safe values for PKU management procedures. For instance, while recommended blood phe level at birth in UK is >400mM, it is set at >600mM in America, Germany and France. By managing phe levels, beneficiaries of early PKU detection can lead a normal life. As evidence, since initiation of a low-phe diet soon after birth in the 1960s, there is a worldwide population of approximately 50,000 individuals suffering PKU with cognitive ability in the normal range (Macleod & Ney, 2010).

Plan of Care

Effective treatment of PKU requires the combined effort of medical professionals including physicians, dieticians and psychologist for patient counselling. This care plan shall be advised by updated recommendations for PKU treatment as designated by Lichter-Konecki (2019).

Treatment objectives.

Main treatment objectives will include:

• To stabilize plasma phenylalanine levels
• Establish dietary plan for management of phe levels
• Provide psychological support

Interventions.

Measure and record baseline temperature, pressure, respiration (T. P. R.). Monitor frequently as patient condition dictates

Carry out blood tests and record results in blood flow chard. Test blood for Pterin defect and record results. Attach date to help in monitoring patient progress post dietary modifications

Monitor phe levels daily or record frequency. Phenylalanine samples may be taken via heel prick before a.m. feed

Administer synthetic for formula (insert name). Use daily data sheet to inform feeding recommendations. Confirm feed details with colleague

Introduce natural protein (insert name) when phe level is (insert recorded data) as directed by physician. For breast-feeding mothers offer synthetic feed before breastfeeding. Collaborate with dietician to regulate feed volume in response to prevalent phe levels

• Record intake and output
• Monitor patient weight to evaluate effectiveness of dietary modifications
• Commence psychological support and parental education programs
• Fill patient discharge plan.

Parental Education

Patient age: Infant

Sex: Male

Phenylketonuria (pronunciation fen-ul-key-toe-NU-ree-uh) is a medical condition where the body is unable to digest some components of protein. Some common proteins include milk, cheese, meat, fish and eggs. Protein are made up of building blocks called amino acids. Patients with PKU have either partial or complete inability to break down a type of amino acid called phenylalanine (simply phe). When foods containing protein are taken, some part of the protein is used for body repair and growth. Most of it, however, is left undigested. This results in phe build up in the blood stream. This leads to serious health effects depending on the seriousness of the PKU condition.

For infants with Classic PKU like your child, symptoms of phe accumulation appear only weeks after birth. They include musty body odor, rashes, hyperactivity and delayed development. If left untreated, it results in brain damage. This defines the importance of new-born screenings in hospitals.

PKU is transferred through inheritance. When both parents have PKU, the child inevitably develops the condition. Some parents are carriers of PKU defective genes, like in your case. Although healthy babies can be born by such parents, there are chances of a PKU offspring. PKU varies in severity. Some cases are mild, but Classical PKU is relatively severe. It means more difficulty in breaking down phe amino acids. While in the womb, developing babies make use of their mother's digestive resources. However, after birth, inability to breakdown phe amino acids manifests.

Once a new-born is diagnosed with PKU, compliance to dietary recommendations provided should be followed consistently. In addition, all medical checks should be attended to ensure phe levels are monitored. It is worth noting that phe levels can fluctuate due to development changes and nutrition. Without regular checks, it will be impossible to maintain healthy levels for optimum child development. Additionally, children require education about PKU. This helps in understanding the importance of maintaining a low-phe diet. Parents should use the parental education obtained in hospital to progressively enlighten the child about the health concern. The numerous online sources of information available today can also come in handy in learning more about the condition.

Today, a lot of people are leading completely normal lives thanks to consistency in following medical recommendations. For infants with classic PKU, extra care should be taken to restrict phe intake. Phe is contained in most common foods. It is, however, much higher in concentration in proteins like milk, eggs, cheese, meat etc. Such foods should be strictly limited according to medical recommendations. To compensate for low protein intake and restricted diet, all individuals with PKU require supplementary formulas containing different types of nutrients. When older, extra servings of acceptable fruits and vegetables should be given to the child to maintain good health. It is worth noting that living normally with PKU is now a reality. With consistent adherence to medical recommendations, almost all adverse effects can be averted.

Recommendations for Effective PKU Management

Generally, a healthy diet should comprise of:

• Proteins - To support body growth and repair
• Carbohydrates and fats - To provide energy for growth and everyday activity
• Vitamins and minerals - To maintain proper health

PKU severely affects protein digesti...