Hyperkeratosis, Scales, and Plaques

CLINICAL DIAGNOSTIC MANUAL

Hyperkeratosis is an abnormal thickening of the outermost layer of the skin, known as the stratum corneum. Scales are dry, flaky sheets of skin that peel off, while plaques are elevated, circumscribed areas of skin larger than papules, often associated with inflammation or infection.

These conditions can result from a variety of cutaneous and systemic disorders.

Pathology	Suspected Diagnosis	Confirmatory Diagnosis
Psoriasis	Red plaques with silvery scales, itching, joint pain.	Skin biopsy, physical examination.
Chronic eczema	Dry, scaly areas, itching, history of atopic dermatitis.	Skin biopsy, physical examination, allergy tests.
Fungal infection	Red plaques with an active border, itching, nail involvement.	Skin culture, skin scraping examination.
Seborrheic dermatitis	Yellowish, greasy plaques, itching, scalp involvement.	Physical examination, medical history.
Lichen simplex chronicus	Thickened plaques with intense itching, history of chronic scratching.	Skin biopsy, physical examination.
Lichen planus	Purple plaques, itching, mucosal involvement.	Skin biopsy, physical examination, serological tests.
Solar keratosis	Rough, scaly plaques on sun-exposed areas, risk of malignancy.	Skin biopsy, dermatoscopy.
Pityriasis versicolor	Hypopigmented or hyperpigmented plaques, mild itching.	Skin scraping examination, Wood’s lamp.
Pityriasis rosea	Initial herald patch followed by a Christmas tree-patterned rash, itching.	Physical examination, medical history.
Juvenile plantar dermatosis	Scaly plaques on the soles of the feet, itching.	Physical examination, medical history.
Guttate psoriasis	Eruption of small scaly papules, itching, triggered by infections.	Skin biopsy, physical examination.
Bowen’s disease	Red, scaly plaques, risk of progression to squamous cell carcinoma.	Skin biopsy, dermatoscopy.
Mycosis fungoides	Red, itchy plaques, history of chronic skin lesions.	Skin biopsy, immunohistochemistry.
Ichthyosis	Diffuse skin thickening, fine scales, family history.	Skin biopsy, genetic testing.
Keratoderma	Thickening of palms and soles, pain, itching.	Skin biopsy, physical examination.
Erythroderma	Generalized redness and scaling of the skin, fever, general malaise.	Skin biopsy, blood tests.
Secondary syphilis	Red, scaly plaques, lymphadenopathy, fever.	Serological tests for syphilis, skin biopsy.