IMD WATCH
IMD AND PREGNANCY - CASE STUDY Una Hendroff RD Clinical Specialist Dietitian, National Centre for Inherited Disorders (NCIMD) Adult Service, Dublin Una works with Inherited Metabolic Disorders, at the, Mater Misericordiae University Hospital, Dublin, Ireland. She has more than 18 years of experience in this area and has been working as a dietitian since 1996.
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Phenylketonuria (PKU) is a disorder of protein metabolism arising from a deficiency in the enzyme phenylalanine hydroxylase (PAH). It is a genetically inherited condition requiring adherence to a phenylalanine (Phe) restricted diet for life.1,2
Figure 1: PKU basis simplified
Maternal PKU (MPKU) requires meticulous management, with stricter adherence to diet recommended prior to conception. Target blood Phe levels during pregnancy are lower than that advised in adulthood, due to the concentration gradient as blood Phe travels across the placenta. MPKU syndrome due to the teratogenicity of high Phe levels in combination with poor adherence to diet, is associated with an increased risk of foetal abnormalities: congenital heart defects, intrauterine growth retardation, microcephaly, development delay and miscarriage.3,4 Long-term outcomes reported include a higher prevalence of learning disability, attention deficit and hyperactivity disorder, anxiety and depression in children born to PKU mums.5 Figure 2: Baby in utero This case study reviews a lady who required gastrostomy feeding before, during and after pregnancy. Limited experience of gastrostomy feeding in MPKU has been reported.6 BACKGROUND This lady was 16 years off the PKU diet on referral with poor adherence in childhood. PKU was diagnosed via newborn screening (initial Phe level: 1,620 microMol/l; genetic mutation: 165T/F39L). She has a younger brother affected and three siblings not affected. Co-morbidities included: depression and anxiety; polycystic ovarian syndrome; hypothyroidism; B12 deficiency; a history of severe obesity (BMI 45.6kg/m2) and symptoms of malnutrition including hair loss. Socially there were many challenges including: being taken into care in childhood, history of homelessness, unemployment, heavy smoking and occasional alcohol intake. She had previously been assessed with poor literacy skills and a borderline learning disability. She had resided in sheltered housing with extensive community supports since the age of 19.
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IMD WATCH Achalasia was diagnosed post inpatient admission following a persistent pattern over 10 months of weight loss (40% of body wt.), gastritis, vomiting and nausea. Figure 3: Achalasia
Achalasia is a condition of unknown aetiology, where the lower oesophageal sphincter muscle fails to relax, leading to dysphagia and regurgitation of foods, often requiring surgery to alleviate symptoms. Medical treatment required the placement of a Radiologically Inserted Gastrostomy (RIG) for nutritional support prior to surgery. The PKU diet was being introduced prior to this and the discharge plan included a feeding regimen adapted for PKU in combination with a minimal oral liquid diet. Tube feeds using a bolus delivery method consisted of: Phe-free protein substitute; whole protein feed; and protein free energy supplement. Six weeks post discharge this lady presented in metabolic clinic with a positive pregnancy and therefore surgery was cancelled. Aims of treatment: • Aim for acceptable Phe levels during pregnancy to avoid toxicity associated with MPKU Syndrome: 150-250mmol/l (NCIMD, target range pre 2016). • Provide sufficient calories, protein and micronutrients to support growth of the developing baby, meet maternal requirements and replenish nutrient stores. • Provide a gastrostomy feeding regimen that patient is able to understand and implement. • Link in with community and hospital teams to provide the necessary support. MONITOR AND REVIEW Dietetic management during pregnancy • Patient sent microtube blood levels for analysis twice weekly with phone follow-up to advise on dietary changes. • Monthly outpatient review for nutritional assessment, intervention and ongoing education. • Minimal oral diet was tolerated intermittently providing additional fluids, energy and some natural protein (0-4ex) daily. • The composition of gastrostomy feeds was adjusted during the course of her pregnancy to meet changes in nutritional requirements. • Weight gain from 4/40-40/40wks gestation was within the acceptable range (IOM7).
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Table 1: weight gain and nutritional intake from PKU adjusted Tube Feed + PO diet
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Gestation wks 2wks PreConception
Weight kg
Natural protein g
Synthetic protein g
Kcals via tube feed
Kcals via estimated oral intake
62.7
40
34
1800
+200-500
5/40
58.3
35
50
1900
+200-500
10/40
59.4
15
67
1688
+200-500
15/40
60
28
50
2111
+200-500
18/40
62.8
32
50
2236
+200-500
27/40
65.3
28
50
2212
+200-500
30/40
67
36
50
2219
+200-500
34/40
70.2
38
50
2267
+200-500
39/40
71.5
40
42
2234
+200-500
4wks Post Delivery
62.2
24
67
2082
+200-500
Figure 4: Graph of Phe levels and protein intake over time
NUTRITIONAL CONSIDERATIONS This lady has poor literacy skills, memory and concentration lapses. Dietary education and follow-up required intensive dietetic and MDT support. The supervised housing complex had limited facilities. Personal hygiene and care of the gastrostomy were also a challenge. Other issues during pregnancy included: • four maternity hospital admissions and linking in with hospital dietitian and staff; • poor compliance with the avoidance of certain solid foods to avoid reflux; • gastrostomy site infections and monthly fluid replacement to anchor feeding tube; • gastrostomy replacement @ 30/40wks gestation; • regular psychological support and community social work input; • liaison with community key workers, public health nurse and local pharmacy. Outcome A baby boy was born via normal delivery at full term with good centile measurements.8 Length: 50cm (9th-25th centile), Weight: 3.14kg (9th-25th centile), head circumference: 35cm (50th centile) Dietetic management postpartum Mum chose to bottle feed her baby and she continued to require gastrostomy feeding in combination with minimal oral diet prior to surgery. The gastrostomy tube was removed during the surgical procedure (Heller’s Myotomy), three months post-delivery and the patient struggled to maintain her PKU diet thereafter. She continues to require ongoing support from the metabolic multidisciplinary team (MDT) and is still engaged with the service. 4 EVALUATION There is limited literature on the dietary management and pregnancy outcomes for women with PKU requiring gastrostomy feeding during pregnancy. Close monitoring and regular communication between both the hospital and community MDT is needed to ensure optimal Phe levels, normal growth and improved outcomes for the developing baby. www.NHDmag.com October 2017 - Issue 128
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