A comprehensive theory of the Lamb shift in light muonic atoms such as $\mu \mathrm{H}$, $\mu \mathrm{D}$, ${\mu }^3{\mathrm{He}}^{+}$, and ${\mu }^4{\mathrm{He}}^{+}$ is presented, with all quantum electrodynamic corrections included at the precision level constrained by the uncertainty of nuclear structure effects. This analysis can be used in the global adjustment of fundamental constants and in the determination of nuclear charge radii. Further improvements in the understanding of electromagnetic interactions of light nuclei will allow for a promising test of fundamental interactions by comparison with “normal” atomic spectroscopy, in particular, with H-D and ${}^3\mathrm{He}\text{−}{}^4\mathrm{He}$ isotope shifts.

• Received 20 January 2023

DOI:https://doi.org/10.1103/RevModPhys.96.015001