Corn (clavus, referred to as corn in Chinese medicine) and callus are localized hyperkeratoses caused by prolonged excessive pressure or friction on the skin. They primarily occur on the hands, feet, fingers, or toes in areas subjected to friction or pressure. Corn presents as a conical hyperkeratosis, while callus appears as a patch-like hyperkeratosis. Corn is often painful and can impair hand or foot function; callus is typically a occupational marker, usually asymptomatic and non-functional, though severe cases may develop rhagades.

bubble_chart Etiology

Shoes and boots that are too tight, along with foot bone deformities, cause excessive compression and friction on the feet. Over time, the keratin gradually proliferates and grows inward, forming a conical keratin plug with its tip pointing inward. People who walk or stand for long periods are more prone to developing this condition. Some cases are also related to grade I puncture wounds.

bubble_chart Clinical Manifestations

1. Corn

1. The lesion appears as a conical keratinous thickening ranging from mung bean to pea size, with a yellowish or dark yellow color. The base faces outward, the surface is smooth and slightly translucent, showing skin lines, with clear boundaries. It is level with or slightly elevated above the surrounding skin, and the tip extends deep into the skin. Beneath it, a thin gray-white membrane (the corn synovial membrane) may sometimes be seen.
2. There is obvious tenderness, and when walking, the sharp, hard tip presses against the sensory nerves in the dermal papillary layer, causing pain.
3. It commonly occurs in areas frequently subjected to friction and pressure, such as the outer side of the little toe, the inner edge of the toes, or the weight-bearing points on the front of the sole. When occurring between the toes, the lesion may become macerated and softened due to the warm and damp conditions in the interdigital space.
4. It is more common in young males.

1. The lesion presents as a light yellow, flat or slightly raised hyperkeratotic patch or plaque with indistinct edges, a smooth surface, and clear skin lines.
2. It commonly occurs on the prominent, pressure-bearing, and friction-prone areas of the palms and soles.
3. There are no subjective symptoms or tenderness.

bubble_chart Diagnosis

1. Hyperkeratosis occurs in areas subjected to pressure and friction. Corns are conical in shape; calluses are irregular, waxy-yellow keratin patches that are thicker in the center and thinner at the edges, with diameters up to several centimeters. They lack a keratin plug, have a smooth surface, clear skin lines, indistinct borders, and often appear symmetrically, most commonly on the heels and weight-bearing areas of the forefoot.
2. Corns exhibit significant tenderness upon pressure, whereas calluses are either asymptomatic or only mildly tender.

bubble_chart Treatment Measures

1. Correct deformities, wear appropriate shoes, and use soft insoles.
2. Medications to exfoliate keratinized tissue.
3. Surgical removal or cryotherapy with liquid nitrogen, laser treatment.
4. Callus generally does not require treatment; thicker ones can be softened with hot water first, then partially shaved off with a blade.

bubble_chart Cure Criteria

1. Cure: The conical keratinous hyperplasia of the corn completely disappears, tenderness is absent, and there is no recurrence.
2. Improvement: The keratinous hyperplasia of the corn is reduced, and tenderness is alleviated.
3. No improvement: There is no change in the keratinous hyperplasia of the corn or tenderness.

bubble_chart Prevention

1. Shoes and boots should be moderate and soft. Those with bone deformities or exostoses should be treated promptly.
2. Local treatment can refer to common warts.