What are the primary differential diagnoses for hyperkeratotic lesions on the sole of the foot in an elderly female patient?

Differential Diagnoses for Hyperkeratotic Lesions on the Sole of the Foot in an Elderly Female

The primary differential diagnoses for hyperkeratotic lesions on the sole of the foot in an elderly female patient are corns (heloma durum), calluses, and neurovascular hyperkeratosis, with corns being the most common painful presentation and calluses representing diffuse thickening without a central core. 1

Primary Differential Diagnoses

Corns (Heloma Durum)

• Corns present as hard, yellow lesions with a central nucleus or plug of keratin that extends downward in a cone-shaped point, causing notable pain that patients often describe as walking on a small stone or pebble. 1
• These lesions typically occur on the tips of toes or underneath the metatarsal heads on weight-bearing surfaces. 1
• The central core distinguishes corns from other hyperkeratotic lesions and is responsible for the characteristic pain pattern. 2

Calluses

• Calluses appear as diffuse thickened areas without a central core and are generally less painful than corns, enlarging with continuing friction as a direct hyperproliferative response of keratinocytes. 1
• In elderly females, calluses are particularly common, with 60% of older people having at least one plantar hyperkeratotic lesion, and females are 2.86 times more likely to develop these lesions compared to males. 3
• The most common pattern is "roll-off" hyperkeratosis on the medial aspect of the 1st metatarsophalangeal joint, accounting for 12% of all lesion patterns. 3

Neurovascular Hyperkeratosis

• Neurovascular hyperkeratosis is a specialized form of callus where nerve endings and blood vessels become prominent in the epidermis in response to trauma, presenting as sensitive, painful areas that bleed with normal debridement. 1
• This typically affects skin overlying the calcaneum and hallux. 1
• Aggressive debridement should not be performed without first ruling out neurovascular hyperkeratosis, as this causes severe pain and bleeding. 1

Secondary Differential Diagnoses to Consider

Focal Palmoplantar Keratoderma

• This is an inherited or acquired disorder causing localized hyperkeratosis, distinguished by distribution pattern and family history. 1
• Unlike corns and calluses that develop from mechanical pressure, keratoderma has a genetic or systemic etiology. 1

Porokeratosis (Rare but Important)

• Porokeratosis ptychotropica can present as symmetrical reddish to brown-colored hyperkeratotic, verrucous plaques, though typically on perianal and gluteal regions rather than soles. 4
• Early skin biopsy is essential because malignant change occurs in 7.5% of porokeratotic lesions. 4
• Disseminated superficial actinic porokeratosis occurs mainly in women on the extremities as atrophic patches rimmed by a ridge of keratin. 5

Squamous Cell Carcinoma

• Biopsy is mandatory before aggressive debridement of suspicious lesions to exclude malignancy. 1
• Any hyperkeratotic lesion that appears atypical, bleeds easily, or does not respond to standard treatment warrants biopsy. 1

Critical Diagnostic Approach

Initial Assessment

• Before performing intralesional steroid injection for resistant hyperkeratotic areas, exclude malignancy by biopsy. 1
• Screen for diabetes and assess for peripheral neuropathy or peripheral artery disease, as these conditions require more cautious management. 1

Key Distinguishing Features

• Paring the lesion helps differentiate: corns reveal a central keratotic plug, calluses show uniform thickening, and neurovascular hyperkeratosis bleeds with minimal debridement. 1
• Lesions under the 1st metatarsophalangeal joint are significantly associated with moderate to severe hallux valgus, whereas lesions under the central metatarsophalangeal joints are significantly associated with deformity of the corresponding lesser toe. 3

Common Pitfalls to Avoid

• Do not assume all hyperkeratotic lesions on the sole are benign corns or calluses—always consider neurovascular hyperkeratosis before aggressive debridement to prevent severe pain and bleeding. 1
• Avoid performing blade debridement if epidermolytic hyperkeratosis is suspected, as this can cause severe complications. 6
• Do not overlook the need for biopsy in atypical or treatment-resistant lesions, as squamous cell carcinoma can masquerade as hyperkeratosis. 1