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.
www.NHDmag.com October 2017 - Issue 128
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