Instrumental Assessment of Plantar Hyperkeratosis in Healthy Subjects and Patients With Diabetes

Inclusion Criteria: * Age ≥ 18 years * Presence of at least one clinically identifiable plantar hyperkeratosis * Intact skin without ulceration * Ability to maintain standing position for at least 30 seconds * Signed informed consent Additional Inclusion Criteria for Diabetes Mellitus Group: * Medical diagnosis of type 1 or type 2 diabetes mellitus * No active foot ulcer * No history of foot ulcer within the previous 12 months Exclusion Criteria: * Active plantar ulcer, pre-ulcerative lesion, or recent ulcer scar * Severe peripheral neuropathy (absence of protective sensation with 10 g monofilament) * Severe peripheral arterial disease (Ankle-Brachial Index \< 0.8) * Foot surgery within the previous 6 months * Active inflammatory, infectious, or dermatological condition at measurement site * Use of keratolytic treatments or debridement within the previous 15 days * Inability to complete the full assessment protocol