THE SUN DOCTOR

Of specialist Your exciting and revealing paper has a line-up your health and general practice doctors waiting to answer in those concerns – and it is for free! So come on, send Doctor deal nagging health bugs and let this week’s Sun your true with it. Yo

DEAR SUN DOC

I have had a black streak line in my thumb fingernail for about a year now. What could be the underlying cause?Simon

Dear Simon,You can get a black streak due to bleeding under the nail as a result of injury or if you are taking blood thinning medication. You can also get a dark line as a result of other health conditions including kidney disease, lung disease, problems with blood circulation or endocarditis (infection of the inner lining of the heart). You may also have melanonychia, darkening caused either by activation of melanocytes (cells that produce the pigment melanin) or by increase in the number of melanocytes.The melanocytes can be activated due to genetics (higher incidence of streaks in people from dark-skinned races), pregnancy, poor nutrition, infections, inflammatory diseases, systemic illnesses, injury, medication such as chemotherapy, HIV medication and some malaria medications.Where there is increased multiplication of the melanocytes, it may be noncancerous such as where there is a mole; or it may be cancerous, and a sample of the tissue needs to be taken to determine which it is.Most of the time, depending on the underlying cause, the darkening of the nail may be harmless and not require any treatment. Where treatment is needed, it will depend on the cause.