What do two brown lines on the thumb region suggest?

Hello,

Welcome to icliniq.com.

I went through your query and understood your concern.

According to your description and the picture shared (the attachment was removed to protect the patient's identity), you have longitudinal melanonychia or linear pigmented lines. The presence of linear pigmented lines on the nails can be due to multiple causes. In white people, the presence of these pigmented lines is considered abnormal and requires thorough assessment, including biopsy. In dark-skinned people, it is a common variant. The most common cause of these lines is a racial factor. Other causes include intake of drugs, trauma, lichen planus, subungual nevi, and malignant melanoma.

Do not worry about it, but do watch the pigmentation. If you notice any variation within the pigmented line or pigmentation on the adjacent nail fold or finger pulp, consult a dermatologist for further evaluation.

I hope this has helped you.

Thanks and regards.