Differential Diagnosis for Pruritus in an 80-year-old Male
- Single most likely diagnosis
- Dry skin (xerosis): Given the patient's age and the fact that the pruritus is more prominent at night and has been consistent for a long time, dry skin is a common condition in the elderly that can cause such symptoms. The mild improvement with Zyrtec may suggest some allergic component, but dry skin is a more straightforward explanation.
- Other Likely diagnoses
- Eczema (atopic dermatitis): Although the patient denies new medications or changes in detergents, eczema can present at any age and may have a variable course. The use of shampoo as soap could potentially irritate the skin, contributing to eczema.
- Psoriasis: This chronic skin condition can cause pruritus, especially on the arms and back. The patient's long-standing symptoms could be consistent with psoriasis, although the lack of other characteristic symptoms like thickened skin or joint pain makes it less likely.
- Allergic contact dermatitis: Despite the patient's denial of new exposures, it's possible that an allergen is causing the reaction, especially given the mild improvement with Zyrtec.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Hematologic malignancies (e.g., lymphoma, leukemia): Pruritus can be a presenting symptom of certain blood cancers. Although rare, missing such a diagnosis could have severe consequences.
- Thyroid disorders: Both hyperthyroidism and hypothyroidism can cause pruritus. Given the potential severity of untreated thyroid disorders, it's crucial to consider these conditions.
- Cholestasis: Obstructive liver disease or primary biliary cirrhosis can cause severe pruritus. This diagnosis is less likely but would have significant implications if missed.
- Rare diagnoses
- Neurological disorders (e.g., neuropathy, multiple sclerosis): Certain neurological conditions can cause pruritus, often in a dermatomal distribution. These diagnoses are less likely but should be considered if other explanations are ruled out.
- Parasitic infestations (e.g., scabies, lice): Although the patient's presentation doesn't strongly suggest a parasitic infestation, these conditions can cause severe pruritus and should be considered, especially if other diagnoses are excluded.