The present invention relates to protein nanocages comprising a melanocyte-targeting moiety and pharmaceutical compositions comprising the protein cages as well as methods for treating or diagnosing hyperpigmentation disorders or other melanocyte-related disorders using the protein nanocages or pharmaceutical compositions. In the preferred embodiment, the protein nanocage is composed of Bacillus stearothermophilus E2 protein of pyruvate dehydrogenase multi-enzyme complex (E2), with a skin penetrating and cell permeating SPACE moiety, and a melanocyte-targeting moiety of alpha melanocyte stimulating hormone.
