I have noticed about a month ago, a dark vein at the back of my 6yr old son s leg, just below his knee joint, right at the top of his calf. He has been diagnosed with environmental asthma and is on a daily medication called Singulair. Is this vein normal or could it be a side effect of his asthma meds, or could it be something different all together. Kind regards, Worried Mother
Thank you for posting your question. The location on the leg that you have mentioned does harbor a major vein. It is most likely that this prominence that you have noticed is a normal occurrence. Also, the Chat Doctor.  Having said that, I would suggest you keep a watch for appearance of any new symptoms like swelling of the legs or appearance of new prominent veins. If so, consulting a doctor would be necessary. If you have any more doubts regarding this case, do write back.