A patient with anti-aquaporin 4 antibody presenting hypersomnolence as the initial symptom and symmetrical hypothalamic lesions.

Here we report a case with positive serum anti-aquaporin 4 (AQP4) antibody who presented with hypersomnolence, symmetrical hypothalamic lesions and a reduced CSF orexin (hypocretin) level without optic nerve and spinal cord lesions on MRI. All of the symptoms, MRI finding and CSF orexin level improved simultaneously after steroid therapy. AQP4 is a member of the AQP superfamily which is strongly expressed in the hypothalamus where orexin (hypocretin)-containing neurons are primarily concentrated. Although there have been only a few reports similar to our case, the present case suggests a close relationship between the positive serum anti-AQP4 antibody and symmetrical hypothalamic lesions with hypersomnolence and without optic /spinal lesion, which is improved by steroid treatment.