Filing too deeply in the corners of the nails can lead to which of the following issues?

Filing too deeply in the corners of the nails can lead to ingrown nails because this practice disrupts the normal growth pattern of the nail. When the corners of the nails are overly filed, the edges of the nails can start to grow into the surrounding skin. This encroachment can irritate the skin and lead to inflammation, resulting in a painful condition known as an ingrown nail. Ingrown nails are particularly common in the toes, but can also occur in fingernails, particularly when proper filing techniques are not followed.

Other issues like hangnails, fungal infections, and discoloration can arise from various factors, but they are not directly caused by filing deeply in the corners specifically. For instance, hangnails are often a result of dry skin or improper nail care, while fungal infections may stem from moisture trapped under nails or in nail beds rather than nail filing practices. Discoloration can also result from other external factors or health conditions, rather than the mechanical action of filing.