Irreversible neurological effects of late diagnosis phenylketonuria: A case presentation

Phenylketonuria (PKU) is an autosomal recessive hereditary disorder due to deficiency of enzyme phenylalanine hydroxylase or the cofactor tetrahydrobiopterin. Its late manifestation leads to irreversible neurological changes. The aim of our work is to emphasize the difference in presentation in late diagnosis of the disease verses classical presentation making it difficult to correctly diagnose and also point out the reasons for late diagnosis and missed cases in India. A 9-year-old patient presented with global developmental delay and severe behavioral problems. Hypertonia and spasticity with low intelligence quotient (IQ) were seen. Baseline investigations such as renal function, thyroid function, electrolytes, uric acid, folate, and blood adrenocorticotropic hormone level were within range; hence, magnetic resonance imaging (MRI) was advised which revealed areas of bilateral demyelination suggesting metabolic leukodystrophy. PKU was thereafter confirmed with metabolic profile and clinical exome study. Early routine screening of all new-borns for common inherited and metabolic disorders should be mandatory to later prevent irreversible damage. Cases of delayed diagnosis deviate considerably from classical clinical and radiological findings of the disease making correct and prompt diagnosis difficult. Education of parents and prenatal counseling should be encouraged.