The challenges of managing coexistent disorders with phenylketonuria: 30 cases

Introduction: The few published case reports of co-existent disease with phenylketonuria (PKU) are mainly genetic and familial conditions from consanguineous marriages. The clinical and demographic features of 30 subjects with PKU and co-existent conditions were described in this multi-centre, retrospective cohort study. Methods: Diagnostic age of PKU and co-existent condition, treatment regimen, and impact of co-existent condition on blood phenylalanine (Phe) control and PKU management were reported. Results: 30 patients (11 males and 19 females), with PKU and a co-existent condition, current median age of 14 years (range 0.4 to 40 years) from 13 treatment centres from Europe and Turkey were described. There were 21 co-existent conditions with PKU; 9 were autoimmune; 6 gastrointestinal, 3 chromosomal abnormalities, and 3 inherited conditions. There were only 5 cases of parental consanguinity. Some patients required conflicting diet therapy (n = 5), nutritional support (n = 7) and 5 children had feeding problems. There was delayed diagnosis of co-existent conditions (n = 3); delayed treatment of PKU (n = 1) and amenorrhea associated with Grave's disease that masked a PKU pregnancy for 12 weeks. Co-existent conditions adversely affected blood Phe control in 47% (n = 14) of patients. Some co-existent conditions increased the complexity of disease management and increased management burden for patients and caregivers. Conclusions: Occurrence of co-existent disease is not uncommon in patients with PKU and so investigation for co-existent disorders when the clinical history is not completely consistent with PKU is essential. Integrating care of a second condition with PKU management is challenging.