Beriberi is a disease caused by a deficiency of thiamine (vitamin B1). This can be due to reduced intake, or a problem with thiamine absorption. Beriberi can exist as wet beriberi, which is when it mainly affects the cardiovascular system causing high-output heart failure with symptoms like dyspnea, and peripheral edema. There can also be dry beriberi, causing symptoms like wasting, and paralysis due to nerve damage. Dry beriberi usually presents with peripheral neuropathy, confusion, and nystagmus (involuntary eye movements).