The patient was an 8-year-old Japanese girl with Gilbert's syndrome (GS). Based on the DNA analysis, she was homozygous for a T-to-G transversion at nucleotide position 1456 in the UGT1A1 gene, leading to the substitution of aspartate for tyrosine at position 486 of the UGT1A1 enzyme. Because this mutation is located in an exon common to UGT1A genes, all the UGT1A enzymes may be affected. It is well-known that UGT1A1, UGT1A6 and UGT1A9 enzymes glucuronidate acetaminophen. To evaluate acetaminophen tolerance in the patient, serum acetaminophen levels were determined after oral administration of acetaminophen (15 mg/kg). The maximum serum acetaminophen level reached (12.8 µg/mL) was far below the toxic level. The finding suggested that the usual therapeutic dose of acetaminophen is safe for the GS patient. The combination of mutation analysis in UGT1A1 and acetaminophen loading test may be useful to avoid adverse effect in GS patients.

Preterm WS patients responded well to treatment. Distinguishing WS patients on the basis of different etiologies is important for evaluating the effectiveness of treatment.