Does anyone know what causes your fingernail to rise in the middle?

fingernail still firm, but, has raised ridge toward center, no pain and half moon has grown larger and lopsidedDoes anyone know what causes your fingernail to rise in the middle?
Could be you you have a chronic lung problem


or a liver problem could be that your blood oxygen level is low


see a doctorDoes anyone know what causes your fingernail to rise in the middle?
my doctor told me it was a sign of chronic lung disease. weird huh?

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