Thick Toenails: Usually Fungal, Not Cardiovascular

Thickened toenails (onychauxis) are most commonly caused by fungal infection (onychomycosis). Other causes include trauma, psoriasis, lichen planus, and aging. Cardiovascular disease does not typically cause nail thickening, though severe peripheral arterial disease may produce brittle, slow-growing nails. A dermatologist or podiatrist can confirm the diagnosis with a nail clipping for microscopy and culture.