Palmoplantar dyshidrosis (also known as dyshidrotic eczema): This condition is characterized by small, itchy blisters on the palms and soles, which can lead to deeply pigmented skin due to chronic scratching and inflammation. It's common in older adults and can be exacerbated by various factors, including stress, allergies, and environmental conditions.

Contact dermatitis: This is a type of skin inflammation caused by contact with irritants or allergens, which can lead to itchy, pigmented rashes on the palms and soles. Common culprits include soaps, detergents, and certain metals.
Psoriasis: Although psoriasis can occur anywhere on the body, palmoplantar psoriasis specifically affects the palms and soles, causing thick, scaly, and sometimes pigmented plaques that can be itchy.
Eczema (atopic dermatitis): Eczema can manifest as itchy, pigmented patches on various parts of the body, including the palms and soles, especially in individuals with a history of atopy.

Malignancy (e.g., mycosis fungoides, squamous cell carcinoma): Although less common, certain types of skin cancer can present as pigmented, itchy lesions on the palms and soles. Early detection is crucial for effective treatment.
Infectious diseases (e.g., syphilis, leprosy): Certain infectious diseases can cause skin manifestations, including itchy, pigmented rashes on the palms and soles. These conditions require prompt diagnosis and treatment to prevent long-term complications.

Keratoderma blennorrhagicum: A rare condition associated with Reiter's syndrome, characterized by thick, scaly skin on the palms and soles, which can be itchy and pigmented.
Pityriasis rubra pilaris: A rare skin disorder that can cause orange-red scaling on the skin, including the palms and soles, and can be accompanied by itching and pigmentation changes.