What is the appropriate workup and treatment for a patient presenting with itching?

Workup for Pruritus (Itching)

Begin with a thorough skin examination to distinguish primary dermatologic disease from pruritus without visible dermatosis, as this fundamentally determines the diagnostic and therapeutic pathway. 1

Initial Clinical Assessment

History Elements to Elicit

• Onset, duration, and distribution of itching (localized vs. generalized) 1, 2
• Timing patterns: nocturnal itching with constitutional symptoms (weight loss, fevers, night sweats) suggests lymphoma 3
• Medication review: all prescription, over-the-counter, and herbal remedies to identify drug-induced causes 1
• Travel and exposure history: tick exposure, swimming in lakes/rivers, sexual history, IV drug use 1
• Associated symptoms: fever timing relative to rash, sore throat, systemic symptoms 4
• Personal/family history: atopy, asthma, hay fever, malignancy 4

Physical Examination Priorities

• Complete skin examination including all body surfaces, mucous membranes (oral, genital, perianal), palms, and soles 1
• Distinguish primary lesions from secondary excoriations to identify underlying dermatosis 5
• Assess body surface area (BSA) involvement if rash present 1
• Examine for blister formation and oral mucosal involvement 1

Laboratory Workup

First-Line Screening Tests

For generalized pruritus without obvious dermatologic cause, obtain: 1, 6, 7

• Complete blood count with differential (assess for eosinophilia, polycythemia, lymphoma)
• Comprehensive metabolic panel (renal and hepatic function)
• Thyroid function tests (TSH) only if additional clinical features suggest thyroid disease 1
• Fasting glucose or HbA1c (diabetes screening)
• Chest X-ray if constitutional symptoms present

Important caveat: Routine endocrine investigations including thyroid testing are not recommended unless additional clinical features suggest endocrinopathy, as thyroid disease rarely causes isolated pruritus (only 27% of thyroid patients have pruritus) 1

Second-Line Investigations (Guided by Clinical Suspicion)

• If age >60 years with diffuse itch <12 months duration: heightened concern for malignancy requires age-appropriate cancer screening 6
• If cholestasis suspected: liver function tests, hepatitis serologies 1
• If HIV risk factors: HIV testing 1
• If neuropathic pattern: consider dermatology referral for skin biopsy 1
• Elevated eosinophils: may indicate T-helper-2 polarization and predict response to immunomodulators 6

Diagnostic Algorithm by Presentation

Localized Pruritus

Suggests neuropathic etiology - consider dermatology or neurology referral 2

Generalized Pruritus Without Rash

Systematic evaluation for: 1, 2

1. Systemic disease: renal failure, cholestasis, thyroid (if symptomatic), hematologic disorders
2. Drug-induced: review all medications for temporal relationship 1
3. Paraneoplastic: especially if age >60, constitutional symptoms, or abnormal screening labs 1, 3
4. Psychogenic/functional itch disorder: diagnosis of exclusion after comprehensive workup 1, 2
5. Chronic pruritus of unknown origin (CPUO): when no cause identified despite thorough evaluation 2

Pruritus With Rash

• Rule out infection (bacterial, fungal, viral, parasitic - especially scabies in immunocompromised) 1
• Consider drug eruption with medication timeline review 1, 4
• Atopic dermatitis: flexural involvement, personal/family atopy history, xerosis 4
• Contact dermatitis: if previously stable eczema deteriorates 4
• Consider skin biopsy if autoimmune disease suspected or diagnosis unclear 1

Critical Pitfalls to Avoid

• Do not delay treatment for Rocky Mountain Spotted Fever if suspected based on fever and rash pattern - start doxycycline immediately without waiting for confirmatory testing 4
• Do not perform exhaustive malignancy workup routinely - investigations should be guided by thorough history, physical examination, and screening labs 1
• Do not use sedating antihistamines in elderly patients except in palliative care settings due to cognitive side effects 4, 3
• In immunocompromised patients, perform early biopsy rather than prolonged empiric treatment 4
• Do not assume viral etiology without considering bacterial causes requiring specific antimicrobial therapy 4

Initial Symptomatic Management

Mild Pruritus (While Awaiting Workup Results)

• Topical emollients as first-line therapy 1
• Mild-to-moderate potency topical corticosteroids for localized inflammation 1, 8
• Topical anti-itch remedies: refrigerated menthol, pramoxine, phenol 1, 9
• Counsel on avoiding skin irritants and maintaining short nails 1, 4

Moderate-to-Severe Pruritus

• Oral antihistamines for symptomatic relief 1
• For lymphoma-associated pruritus: cimetidine, gabapentin, carbamazepine, mirtazapine, or phototherapy 3
• For severe pruritus without rash: consider gabapentin, pregabalin, aprepitant, or dupilumab 1
• Systemic corticosteroids: reserved for severe cases or palliative care in incurable disease 1, 3

Definitive treatment requires addressing the underlying cause - symptomatic management alone is insufficient for long-term control 3, 7