Primary cutaneous amyloidosis is characterized by polymerization of extracellular amyloid precursors in β-pleated sheet conformation into larger fibrillar aggregates. Observation in models of Alzheimer's disease have noted that amyloid polymerization in the brain is blocked by reactive oxygen species. Singlet oxygen is formed in the skin during methyl aminolevulinate photodynamic therapy. Therefore, we speculate that type II photochemical reaction is responsible for the observed therapeutic activity of methyl aminolevulinate photodynamic therapy in our patient with primary cutaneous amyloidosis. Our case is the first report demonstrating the efficacy of daylight photodynamic therapy in primary cutaneous amyloidosis. Daylight photodynamic therapy may provide a convenient and cost-effective therapeutic option in primary cutaneous amyloidosis, and its efficacy should be further confirmed in prospective trials.