Kim et al. [27] found that miR-1299 is downregulated in melanin deposition diseases, including chloasma, and its expression level is inversely proportional to that of ARG2. ARG2 is expressed in diverse extrahepatic tissues lacking a complete urea cycle, including skin keratinocytes and fibroblasts, and can reduce the degradation of melanosomes to increase pigmentation [78]. The gene discussed is ARG2; the disease is freckles.