The amino acid residues affecting the function of rat sterol 14-demethylase P450 (CYP51) were examined by means of point mutation. Forty-five mutants with respect to 27 amino acid sites were constructed and expressed in Escherichia coli Substitution of highly conserved Y131, E369, R372, or R382 decreased the expression of CYP51 protein, indicating some structural importance of these residues. Substitution of H314, T315, or S316 caused considerable effects on the catalytic activity, and T315 was identified as the “conserved threonine” of CYP51. H314 was important for maintenance of the activity of CYP51 and was a characteristic residue of this P450, because the position corresponding to this residue is occupied by an acidic amino acid in most other P450 species. A144 was identified as a residue affecting the interaction of CYP51 with ketoconazoe. Substitution of A144 with I, which occupies the corresponding position in fungal CYP51, enhanced the ketoconazole susceptibility of rat CYP51 with little change in the catalytic activity, indicating an important role of this residue in determination of the ketoconazole susceptibility of CYP51. Alteration of the catalytic activity was caused by the substitution at some other sites, whereas substitution of a few highly conserved amino acids caused little alteration of the activity of CYP51.

We experienced a 6-year-old case of drug-induced hypersensitivity syndrome (DiHS)/drug reaction with eosinophilia and systemic symptoms (DRESS) with subsequent development autoimmune thyroiditis (Hashimoto’s thyroiditis), type 1 diabetes with antithyroglobulin, thyroid peroxidase, insulinoma-associated antigen and anti-insulin antibodies at 4 months, alopecia at 7 months, vitiligo, uveitis due to Vogt-Koyanagi-Harada disease at 8 months after clinical resolution of the DiHS/DRESS. He was diagnosed as type III polyglandular autoimmune syndrome (PASIII) after DiHS/DRESS. Prompted by this case, we sought to determine which triggering factors were responsible for later development of PASIII in previously published cases with autoimmune sequelae. In the literature review, five patients with DIHS/DRESS were found to develop autoimmune sequelae consistent with PASIII. All cases with PASIII were much younger than those without them. Four out of the five patients were treated with intravenous immunoglobulin or pulsed prednisolone in the acute stage, although effective in short-term outcomes.