Efficacy of topical dimethyl sulfoxide (DMSO) 50% solution vs tretinoin 0.5% cream in treatment of patients with primary macular amyloidosis: A split‐side single‐blinded randomized clinical trial

Primary localized cutaneous amyloidosis (PLCA) is a recalcitrant sporadic dermatological condition and most treatments have failed so far. We studied the efficacy of topical dimethyl sulfoxide (DMSO) 50% solution in comparison with tretinoin 0.5% cream in treatment of macular amyloidosis. In this split-side within-person single-blinded randomized clinical trial, 18 patients with bilateral macular amyloidosis received topical DMSO 50% solution and tretinoin 0.5% cream either on their right or the left side. The colorimetry, pruritus scoring, and photography were done. A significant pigmentation decline per each follow-up was observed in DMSO group compared to the tretinoin group (tretinoin: -1.31 vs DMSO: -7.34; difference in slopes: -6.03 [95% confidence interval: -12.06 to -0.01], PInteraction = .049). An insignificant diminution trend in pigmentation was observed for both treatments (Ptretinoin = .672, PDMSO = .092). Also, both treatments relived itchiness, but DMSO completely dispatched itchiness from the first follow-up (P = .003 for tretinoin and <.0001 for DMSO). In conclusion, our results showed DMSO and tretinoin cream have the positive effect on the both pigmentation and itchiness in PLCA. DMSO may be more beneficial than tretinoin, since DMSO was significantly better in reducing itchiness. More investigations are warranted to provide sufficient evidence.