Résumé
BACKGROUND: Tyrosinase is the critical enzyme in melanin synthesis. DOPA staining has been used as a standard assay for detecting tyrosinase activity, but it exhibits several limitations. Tyramide based tyrosinase assay (TTA) is a simple and sensitive tyrosinase detecting method. OBJECTIVE: This study aimed to compare the stainability of pigmentary disorders using TTA and DOPA staining. METHODS: The subjects were composed of hyperpigmentary disorders (n=10), hypopigmentary disorders (n=7), and alopecia areata (n=7). The colocalization study of TTA and Mitf using immunofluorescence was performed on alopecia areata. DOPA staining was performed on all tissues to compare with TTA immunohistochemistry. RESULTS: TTA positive cells were correlated with Mitf positive cells in the tissue of alopecia areata. In hyperpigmentary disoders, TTA was stronger than DOPA staining. TTA and DOPA staining didn't observe the positive cells in lesion of vitiligo and piebaldism, but both showed the positive cells in normal skin. TTA staining showed positive cells in the transitional lesion of vitiligo but, DOPA staining did not. In alopecia areata, TTA positive cells were observed, but DOPA staining did not. CONCLUSION: TTA is more sensitive than DOPA staining in pigmentary disorders for detecting tyrosinase activity.