Circumscribed palmar hypokeratosis.

Area of Science:

• Dermatology
• Histopathology
• Clinical Diagnosis

Background:

• Circumscribed palmar hypokeratosis is a rare, benign dermatosis affecting the palms.
• It presents as a well-demarcated, erythematous, and slightly depressed or thickened skin patch.
• Diagnosis is primarily based on characteristic clinical and histopathological findings.

Observation:

• A 66-year-old woman exhibited a 40-year history of a slowly enlarging erythematous patch on her left thenar eminence.
• Clinical examination revealed a sharp demarcation, or 'step,' between the affected and unaffected skin areas.

Findings:

• Histopathological examination demonstrated a distinct 'step' sign at the junction of normal and abnormal skin.
• Crucially, features such as epidermal dysplasia and the presence of a cornoid lamella were absent.
• These histopathological findings are typical for circumscribed palmar hypokeratosis.

Implications:

• The study emphasizes the importance of recognizing the characteristic histopathological 'step' sign for accurate diagnosis.
• Differentiating circumscribed palmar hypokeratosis from other palmoplantar conditions is essential for appropriate patient management.
• This case contributes to the understanding of the clinical spectrum and diagnostic criteria for this uncommon condition.