Sp r june 2011phenylketonuria and other inherited metabolic disorders

Phenylketonuria and other inherited metabolic disorders
Kathleen Williams
Diabetes and Obesity Specialist Dietitian
South Devon Healthcare

Phenylketonuria – an autosomal recessive disorder caused by a deficiency of phenylalanine hydroxylase
Leads to increased blood phenylalanine
Hyperphenylalaninaemia leads to neurotoxicity
1:4 incidence
Prevalence 1/10,000
Guthrie Test
Phenylketonuria

Phenylketonuria (PKU)

Classical – levels >1200 mcmol/l
Moderate – levels >600 – 1200 mcmol/l
Mild - >400 mcmol/l
Normal Phe level – 120 -600mcmol/l
Untreated PKU – mental retardation, hyperactive behaviour with autistic features, seizures

Restrict dietary Phe
Allocate an allowance of Phe containing foods
Provide a Phe free amino acid substitute
Maintain energy intake with low protein foods
Ensure mineral and vitamin intake adequate
Dietary Treatment of PKU

Fats – butter, margarine, oils
Sugar – jam, honey ,boiled sweets, cornflour
Drinks – Lucozade, lemonade, squash, tonic water, soda water, tea, coffee
Herbs and spices
Free foods

Fruits – most except bananas
Vegetables – most except for potatoes, sweet potato, peas, beans, sweetcorn,
May need to count if eat a lot and need to be strict
Low/negligible Phenylalanine content

1 Phe exchange = 50mg Phe or 1g protein
Cows milk 30ml
Chips 25g
Baked beans 20g
Cornflakes 10g
Rice – cooked 45g
Banana 100g
Phenylalanine Exchanges

Meat, fish, cheese, eggs, nuts
Milk and yogurt
Ordinary cereals, bread and flour (unless counted as an exchange)
Foods to avoid

See as a life long diet
Phe levels can affect concentration and behaviour
Effective contraception
Pregnancy
Difficulties in maintaining diet
??Follow up in clinic
PKU in treated adults

Evidence that implementing Phe restriction can help with skin conditions, behaviour and seizures
Difficult to implement and monitor
Realistic and achievable
Effective contraception
Julie and Sandi
PKU in untreated adults

Essential to achieve and maintain Phe levels
60 – 250mgmol/l pre-conception and throughout pregnancy
Levels above 900mgmol/l at conception – high risk of malformation
Monitor 2x/week
Maternal PKU

Treated but often had levels above target
Worked as ECG technician
Continued with some diet restriction but levels usually 700 -1000 from 1989-1996
Continued with a-a substitute
1996 – wanted to become pregnant. Tightened up diet but difficulty maintaining weight.
Kim 22/01/73

Maxamum a-a substitute
Duocal
Maxijul
Low protein products
Phe exchanges
Weight 46.5kg BMI 19
Regime

Regular visits/phone calls
Adjust Phe exchanges up or down according to levels
Increase calories from Duocal or Maxijul to ensure weight gain
Monthly blood tests for a-a profile, tyrosine levels, FBC, ferritin, selenium, zinc, CRP
Letter stating needs IV glucose if has prolonged vomiting
Pregnancies 1997 and 2001

Galactosaemia
Maple Syrup Urine Disease
Organic acidaemias eg proprionoc acideamia and methyl malonic acidaemia
Other inherited metabolic disorders

Galactose – monosaccharide found in milk
Exclude milk and dairy products, lactose fillers eg in medications
Reccommended diet for life
Adult females – late puberty. Most are infertile or reduced fertility
Osteoporosis
Incidence 1/45,000
Galactosaemia

Branched chain a-a (leucine, isoleucine and valine)
Ketonuria, poor feeding, encephalopathy within 4-5 days birth
Life long diet
Adolescents and adults at increased risk of ADHD, depression and anxiety
Pregnancy – frequent monitoring of plasma a-a and growth
Incidence 1/180,000
Maple Syrup Urine Disease

Severity of disorder depends on enzyme activity.
Presents with severe metabolic acidosis, hypotonia, dehydration in early infancy
Poor prognosis if severe with little or no enzyme activity
Organic acidaemias

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Sp r june 2011phenylketonuria and other inherited metabolic disorders

by PeninsulaEndocrine on Aug 12, 2011

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