Pallor and Limb pain

Sam is a 13 year-old boy with a four week history of fatigue and lethargy. When he gets home from school, he lies on the sofa and watches the TV. He used to go out on his bike with his friends, but now says he does not want to. Sam has also noticed that his legs have been achy, particularly his right leg. In the last 3 weeks he has been waking up at night with his legs aching. He was previously very active, cycling and playing football, but is now struggling to take part in sport and physical education classes at school due to tiredness and feeling cold. He has been struggling to recover from repeated viral infections over the last few months. His mother noticed that he has lost weight.

On examination, Sam was thin and looked pale. He had some bruising around his shins and calves. His chest was clear and heart sounds were normal. He had no joint abnormalities on pGALS examination. Abdominal examination showed hepatosplenomegaly.

Sam's GP checked some urgent blood tests and arranged an early follow-up appointment.