IN ASSOCIATION WITH THE NSPKU
Suzanne Ford NSPKU Dietitian for Adults Suzanne Ford is a Metabolic Dietitian working with Adults at North Bristol NHS Trust and also for the National Society of Phenylketonuria).
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CASE STUDY: DIETETIC MANAGEMENT IN ORNITHINE TRANSCARBAMYLASE DEFICIENCY A 34-year-old female with an ornithine transcarbamylase deficiency planned to conceive. This article is an account of dietetic management before and during pregnancy and delivery. BACKGROUND This female patient is a carrier manifest of an X linked urea cycle disorder, ornithine transcarbamylase (OTC) deficiency. She is known to have c.217-1G>A mutation, which is a mutation associated with relatively little enzyme activity. The deficient enzyme places the individual at risk of hyperammonaemia which can lead to encephalopathy and death. Treatment of OTC deficiency is a safe protein diet (i.e. moderately low, with or without essential amino acids and micronutrient supplements), daily ammonia scavengers, an arginine supplement and, finally, glucose polymer emergency regimen to reduce the effects of catabolism.
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This patient has a history of decompensations - critical care and heroic measures were needed; the last hospital admission was at age 33 years old and she is under sixmonthly follow-up with her metabolic team. The patient’s medications were: • Sodium benzoate 16g in divided doses orally; • L-Arginine 6g daily orally; • B12 3 monthly intramuscular injection; • Calcichew D3 forte orally; • Forceval once daily orally. Dietary management centred on a moderate protein restriction; it is possible that the patient was not consistently compliant; she had hospital admissions for management of hyperammonaemia at age 15, 26, and 33. Her use of emergency regime was approximately once per year due to intercurrent illnesses. In inborn errors of metabolism the best outcomes are with planned pregnancy, so, in 2010, the patient and her husband had genetic counselling. They went on to have pre-implantation genetic diagnosis (funding was obtained from clinical commissioners). The patient underwent an obstetric and gynaecological assessment including cyst removal, super-ovulation and egg harvest, then in vitro fertilisation followed by genetic diagnosis of foetus and implantation. This was done twice to no avail. Following this, there was a natural conception of an affected male and termination in April 2015. After the termination, another natural pregnancy occurred, this time found to be female. DIETARY MANAGEMENT PRECONCEPTION AND FIRST TRIMESTER 1. The patient changed from taking a standard multivitamin to pregnancy multivitamin/ mineral, including 400ug folic acid and also an omega-3 supplement (containing 200mg preformed docosohexanoic acid). 2. Frequent detailed dietary assessment based on a preconception weight of 54kg, with advice for an intake of 45g protein (0.83g/kg) and approximately 1,670kcals daily. 3. There was very strong encouragement to take an emergency regimen (of 25% glucose polymer solution every two hours) if experiencing nausea or vomiting, and to contact the metabolic team/seek admission to A & E if this did not work for more than eight hours.
www.NHDmag.com November 2017 - Issue 129
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