OTC and encephalitis: Other reported conditions that mimic HM are all conditions potentially associated with focal neurological deficits (i.e., hypercapnia, hyponatremia, hypocalcemia, hepatic failure, renal failure, meningitis/encephalitis, carotid dissection, antiphospholipid syndrome, systemic lupus erythematosus, and ornithine transcarbamylase deficiency).