Itch: Epidemiology, clinical presentation, and diagnostic workup

Abstract

Itch, or pruritus, is the uncomfortable sensation underlying the desire to scratch. Itch is a very common complaint in the general population that can result from dermatologic, systemic (eg, renal, hepatobiliary, endocrine), paraneoplastic, neuropathic, and psychogenic etiologies. Chronic itch is associated with significant sleep disturbances and profoundly reduces overall quality of life. Certain populations, including elderly and African Americans, are at increased risk of experiencing heightened burden of itch. Because of the variable clinical presentation and wide-ranging etiologies, itch presents a challenge for clinicians. The initial evaluation should include a complete blood count, with differential, hepatic, renal, and thyroid function testing along with diabetes screening. Further testing should be guided by history and physical examination findings. There should be a heightened concern for underlying malignancy in individuals older than 60 years of age who have a history of liver disease and diffuse itch less than 12 months of duration. For individuals with chronic pruritus of unknown origin, increased blood eosinophils may serve as a biomarker of T helper cell type 2 polarization and response to immunomodulator therapies. In this first part of a 2-part continuing medical education series, we describe the broader epidemiology and specific conditions associated with itch and the clinical presentation and diagnostic workup for patients with itch.

Keywords: clinical features; diagnostic workup; epidemiology; itch; pruritus.

Fig 1.

Itch can arise in the context of various systemic, neuropathic, and psychogenic etiologies.

Fig 2.

Neuropathic etiologies of itch. C, Cervical; L, Lumbar; T, Thoracic.

Fig 3.

Various clinical presentations of itch. A and B, Atopic dermatitis. C, Contact dermatitis. D, Psoriasis. E, Prurigo nodularis. F, Grover disease. G, Scabies. H, Dermal hypersensitivity reaction, often referred to as “itchy red bump disease.” I, Lichen planus. J, Pityriasis rubra pilaris. K, Chronic urticaria. L, Mycosis fungoides.

Fig 3.

Various clinical presentations of itch. A and B, Atopic dermatitis. C, Contact dermatitis. D, Psoriasis. E, Prurigo nodularis. F, Grover disease. G, Scabies. H, Dermal hypersensitivity reaction, often referred to as “itchy red bump disease.” I, Lichen planus. J, Pityriasis rubra pilaris. K, Chronic urticaria. L, Mycosis fungoides.

Fig 4.

General approach to itch based on clinical presentation and underlying etiology. These are not absolute categorizations, but represent a general schema.

Fig 5.

Bedside clinical clues suggestive of etiologies of itch.

Fig 6.

Diagnostic workup algorithm of chronic itch.^,,,,,, *Although the consideration of trial treatment with immunomodulary therapy needs further exploration, patients with elevated IgE may also be responsive to immunodulatory therapy. CBC, Complete blood count; CXR, chest x-ray; DIF, direct immunofluorescence; Dx, diagnosis; H&E, hematoxylin and eosin; H&P, history and physical examination; HbA1c, hemoglobin A1c; KOH, potassium hydroxide; LDH, lactate dehydrogenase; MRI, magnetic resonance imaging; ROS, review of systems; SPEP, serum protein electrophoresis; UPEP, urine protein electrophoresis.