Hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC), also known as Andermann syndrome, is a very rare inherited disorder that affects the nerve cells. Symptoms begin appearing in individuals affected by this disorder early in life. They include low muscle tone, absent reflexes, muscle weakness, reduced sensory function in their limbs, intellectual disability, and abnormal development of corpus callosum, which is the tissue connecting the left and right halves of the brain. As individuals age, they may develop contractures and scoliosis. Affected individuals share characteristic facial features which include facial asymmetry, long face, narrow forehead, large ears, drooping of the eyelids, and increased distance between the eyes. Children affected with HMSN/ACC are able to learn how to walk, though at a later age than most children. By adolescence, however, most individuals are wheelchair bound. During adolescence, affected individuals develop hallucinations, psychosis, and other psychiatric symptoms. Death usually occurs in third or fourth decade of life. There is no cure for HMSN/ACC; however medical surveillance and care may help to improve some symptoms and overall condition of life. HMSN/ACC is caused by pathogenic variants in the SLC12A6 gene.