Psychosocial aspects of PKU: hidden disabilities--a review.

Phenylketonuria (PKU) is an inborn error of metabolism, and its detrimental effects on neurocognitive functioning have been well studied. Early detection and treatment of PKU prevent the severe consequences of this disorder. However, even early- and well-treated patients experience hidden disabilities, including subtle deficits in executive functioning, mild reductions in mental processing speed, social difficulties, and emotional problems that may remain unnoticed for years. Poor executive function (EF) may impact treatment adherence and may lead to psychosocial deficits that are not always visible. These psychosocial aspects include social difficulties and psychosocial problems, such as forming interpersonal relationships, achieving autonomy, attaining educational goals, and having healthy emotional development. Studies report EF deficits in children and adults with early-treated PKU, which contribute significantly to the hidden disabilities in this population. In adults, hidden disabilities affect job performance and social relationships as a result of residual attention deficits, poor EF (e.g., planning, organizing), and reduced processing speed. An indirect relationship also exists between quality of life and EF impairment. In the absence of overt psychiatric symptoms, low level depressive or anxious symptom may be present. The interaction between the neurocognitive deficits and psychiatric symptoms puts this population of patients at significant risk for experiencing hidden disability. PKU is a disorder in which a less than optimal psychosocial outcome arises from the cumulative impact of relatively mild symptoms. The key to reducing risks associated with PKU is metabolic control throughout life.

High incidence of hypermethioninaemia in a single neonatal intensive care unit detected by a newly introduced neonatal screening programme.

From 1 January 2007 an expanded neonatal screening programme was initiated in the Netherlands, including homocystinuria with methionine as the primary marker. During the first 2 months hypermethioninaemia was detected in 14 newborns who, after proper evaluation, were demonstrated not to have classical homocystinuria. Remarkably, all these children were admitted to a single neonatal intensive care unit (Academic Medical Center, Amsterdam (AMC-NICU)). We evaluated the possible causes for this finding. The cohort of newborns with hypermethioninaemia (group 1) was compared with the cohort of newborns with normal screening results admitted to the AMC-NICU in the same time period (group 2). In addition, parenteral nutrition protocols from all NICUs in the Netherlands were compared. Mean birth weight and gestational age were significantly lower in group 1 than in group 2. All patients in group 1 received parenteral feeding (TPN) at the time of screening and received a higher mean amino acid intake per kilogram body weight than patients receiving TPN in group 2. Also, the AMC-NICU uses a different amino acid mixture for TPN than the other Dutch NICUs, containing more than twice the amount of methionine per gram of amino acids compared with other mixtures. The high incidence of hypermethioninaemia in the AMC-NICU is explained by a combination of low birth weight, low gestational age, and high protein intake supplied by a specific parenteral amino acid mixture containing large amounts of methionine. To prevent hypermethioninaemia, the use of high-methionine containing solutions for TPN should be reconsidered.