Pruritus: Differential Diagnosis

Table 1: Historical Findings That Suggest Etiologies for Pruritus

HISTORICAL FINDING	POSSIBLE ETIOLOGIES
New cosmetics or creams	Allergic contact dermatitis, urticaria, photodermatitis
New medications, supplements, or illicit drugs	Urticaria, fixed drug eruptions
Recent travel	Pediculosis, scabies infestation, photodermatitis, urticaria
Hobby or occupational exposure to solvents, adhesives, cleaners	Irritant contact dermatitis, xerosis, atopic dermatitis, eczema
New animal exposures	Flea infestation, allergic contact dermatitis, urticaria
Sick contacts, especially those with febrile diseases and rashes	Rubeola, mumps, varicella, scarlet fever, cellulitis, fifth disease, folliculitis
Unexplained weight changes, menstrual irregularity, heat/cold intolerance	Thyroid disease with secondary urticaria or xerosis
Unexplained weight loss, night sweats, unexplained fevers, fatigue	Lymphoma with secondary generalized pruritus
Malaise, nausea, decreased urine output	Renal failure with generalized pruritus

Table 2: Dermatologic Etiologies for Pruritus

ETIOLOGY	FEATURES
Allergic/irritant contact dermatitis	Sharply demarcated, erythematous lesion with overlying vesicles
	Reaction within two to seven days of exposure
Atopic dermatitis	Pruritic area where rash appears when scratched in patients with atopic conditions (e.g., allergic rhinitis, asthma)
	Involvement of flexor wrists and ankles, as well as antecubital and popliteal fossae
Bullous pemphigoid	Initially pruritic urticarial lesions, often in intertriginous areas
	Formation of tense blisters after urticaria
Cutaneous T-cell lymphoma (mycosis fungoides)	Oval eczematous patch on skin with no sun exposure (e.g., buttocks)
	Possible presentation of new eczematous dermatitis in older adults
	Possible presentation of erythroderma (exfoliative dermatitis)
Dermatitis herpetiformis	Rare vesicular dermatitis affecting the lumbosacral spine, elbows, or knees
Dermatophyte infection	Localized pruritus and rash characterized by peripheral scaling and central clearing
	Can occur on several sites, including the feet, scalp, trunk, and groin
Folliculitis	Pruritus out of proportion to appearance of dermatitis
	Papules and pustules at follicular sites on chest, back, or thigh
Lichen planus	Lesions often located on the flexor wrists
	Characterized by the six P's (pruritus, polygonal, planar, purple, papules, plaques)
Lichen simplex chronicus	Localized, intense pruritus
	Initial erythematous, well-defined plaques with excoriations lead to thickened, lichenified, violaceous patches if scratching continues
Pediculosis (lice infestation)	Occiput in school-aged children; genitalia in adults (sexually transmitted)
Psoriasis	Plaques on extensor extremities, low back, palms, soles, and scalp
Scabies	Burrows in hand web spaces, axillae, and genitalia
	Hyperkeratotic plaques, pruritic papules or scales
	Face and scalp affected in children but not in adults
Sunburn	Possible photosensitizing cause (e.g., with use of nonsteroidal anti-inflammatory drugs or cosmetics)
Urticaria (hives)	Intensely pruritic, well-circumscribed, erythematous, and elevated wheals
	Lesions may coalesce and wax and wane over several hours
Xerosis	Intense pruritus, often during winter months in northern climates
	Involvement of back, flank, abdomen, waist, and lower extremities
	More common in older persons

Table 3: Systemic Etiologies for Pruritus

Autoimmune

Dermatitis herpetiformis

Dermatomyositis

Linear immunoglobulin A disease

Sjögren syndrome

Hematologic

Hemochromatosis

Iron deficiency anemia

Mastocytosis

Plasma cell dyscrasias

Polycythemia vera

Hepatobiliary

Biliary cirrhosis

Chronic pancreatitis with obstruction of biliary tracts

Drug-induced cholestasis

Hepatitis, particularly hepatitis C

Sclerosing cholangitis

Infectious disease

AIDS

Infectious hepatitis

Parasitic disease (giardiasis, onchocerciasis, schistosomiasis, ascariasis)

Prion disease

Malignancy

Leukemia

Lymphoma

Multiple myeloma

Solid tumors with paraneoplastic syndrome

Metabolic and endocrine

Carcinoid syndrome

Chronic renal disease

Diabetes mellitus

Hyper/hypothyroidism

Hyperparathyroidism

Neurologic

Cerebral abscess

Cerebral tumor

Multiple sclerosis

Stroke

Other

Drug ingestion

Eating disorders with rapid weight loss

Neuropsychiatric disorders

Pregnancy

References:

1. American Family Physician: A Diagnostic Approach to Pruritus 

http://www.aafp.org/afp/2011/0715/p195.html

2. NCBI Chronic Pruritus and Treatment 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3119985/