A disease caused by determinants arising after birth. This disease is characterised low levels of riboflavin (vitamin B2) leading to low levels of red blood cells in the body. This disease may present with fatigue, muscle weakness, loss of appetite, weight loss, diarrhoea, nausea, fast heartbeat or numbness in extremities. Confirmation is by identification of low levels of riboflavin and low red blood cell count in a blood sample.