TCIRG1 and osteopetrosis: In contrast to a more common form of ARO caused by variants in TCIRG1 encoding the a3 subunit of the vacuolar-type ATPases (15, 16), CLCN7-related osteopetrosis is accompanied by lysosomal storage in neurons and the kidneys (17) and can result in neurodegeneration (15, 18, 19).