Differential Diagnosis for Diffuse Itching in a 35-Year-Old Male

Single Most Likely Diagnosis

• Dry Skin (Xerosis): This is a common condition that can cause diffuse itching, especially in dry environments or during winter months. It's often seen in individuals who frequently wash their hands or are exposed to harsh soaps and detergents.

Other Likely Diagnoses

• Atopic Dermatitis (Eczema): A chronic skin condition characterized by itchy, inflamed skin. It's common in individuals with a history of allergies or asthma.
• Allergic Contact Dermatitis: An allergic reaction to substances like metals (e.g., nickel), latex, or certain chemicals in personal care products, which can cause widespread itching if the allergen is applied over a large body surface area.
• Psoriasis: An autoimmune condition that speeds up the life cycle of skin cells, causing cells to build up rapidly on the surface of the skin. The extra skin cells form scales and red patches that itch or burn.
• Urticaria (Hives): Often caused by an allergic reaction, which can lead to itchy welts on the skin.

Do Not Miss Diagnoses

• Hodgkin Lymphoma: Though rare, some cancers like Hodgkin lymphoma can present with itching as an early symptom, often without a rash.
• Cholestasis: Conditions affecting bile flow, such as primary biliary cirrhosis or bile duct obstruction, can cause severe itching without a primary skin rash.
• Thyroid Disorders: Both hyperthyroidism and hypothyroidism can cause itching, though the mechanism is not fully understood.
• Renal Failure: Uremic pruritus associated with chronic kidney disease can cause severe, diffuse itching.

Rare Diagnoses

• Polycythemia Vera: A rare blood disorder that can cause itching, particularly after warm baths or showers, due to the release of histamine from basophils.
• Mastocytosis: A condition characterized by an accumulation of mast cells in one or more organs, which can cause itching among other symptoms.
• Neurological Disorders: Certain neurological conditions, such as multiple sclerosis or neuropathies, can cause itching sensations without a clear dermatological cause.

Each of these diagnoses should be considered based on the patient's full medical history, physical examination, and potentially, further diagnostic testing.