Brief Answer:
Please refer to the detailed answer below

Detailed Answer:
Hello Sir

After going through the medical details provided by you I understand your concern for your health and I would like to tell you that the most common cause of splincter nails
Is

1. Infection of the heart valves ( infective endocarditis )

Other causes includes

1. Small vessels vasculitis
2 diabetes
3. Local trauma

I would like to suggest you to get one Echocardiography done to rule of infection of the heart valves first as that is more important.

I hope this information will guide you properly.

Kind regards
Dr Bhanu partap

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