“The mechanism of hyper-pigmentation is due to increased melanin synthesis rather than a defect in melanin,” explained the authors.
It should be noted that melanonychia is a nail pigmentation condition that has several underlying causes and occurs due to an increase in the number of melanocytes in the nail.
Bacterial infections, systemic diseases, tumours, and certain drugs may activate the melanocytes and contribute to hyperpigmentation.
Therefore, to understand whether the pigmentation of nails is caused by B12 deficiency, it may be worth relying on other classic symptoms.