Co-occurrence of vitamin D-dependent rickets type 1 and phenylketonuria.

UNLABELLED: Vitamin D-dependent rickets type 1 (VDDR1) was diagnosed in a 15-month-old girl with well-controlled phenylketonuria (PKU). The patient was homozygous for the PAH mutation L249F. The PAH and CYP27B1 genes are both located on the long arm of chromosome 12 and could possibly have been inherited from a common ancestor. The parents were not aware of any ancestral relationship and the patient was compound heterozygous for two different CYP27B1 mutations (R389H and S416X). Her mutations were shown to originate from each of her four grandparents. In Norway, the co-occurrence of PKU and VDDR1 is expected to occur by chance one to two times per billion births.
CONCLUSION: The extremely rare co-occurrence of VDDR1 and PKU requires careful genetic work-up and close attention to family information, but the combined treatment of the two metabolic disorders may not create special problems.