What are the next steps for a patient with a pruritic (itchy) rash that is not responding to corticosteroids (steroids)?

Management of Pruritic Rash Not Responding to Steroids

For patients with a pruritic rash not responding to corticosteroids, the next steps should include a systematic investigation for underlying causes and consideration of alternative treatments such as immunomodulators, antihistamines, or phototherapy based on the suspected etiology.

Diagnostic Approach

When a pruritic rash fails to respond to corticosteroids, consider the following underlying causes:

1. Systemic conditions:

   • Renal disease: Check urea and electrolytes 1
   • Liver disease: Perform liver function tests, consider bile acids and antimitochondrial antibodies 1
   • Neurological causes: Evaluate for neuropathic pruritus 1
   • Infections: Take detailed history including travel, consider HIV and hepatitis serology 1
   • Drug-induced: Review all medications for potential causative agents 1
   • Hematological disorders: Consider lymphoma, polycythemia vera 1
   • Thyroid disease: Check thyroid function, especially in patients with thyroid autoimmunity 1

2. Special considerations:

   • Elderly patients: Consider age-specific causes like asteatotic eczema or bullous pemphigoid 1
   • Autoimmune conditions: May require specific immunological testing

Treatment Alternatives

First-line alternatives:

1. Non-sedating antihistamines:

   • Recommended for generalized pruritus 1, 2
   • Examples: loratadine 10mg daily 2
   • Note: Sedating antihistamines should be avoided in the elderly except in palliative care 1

2. Topical alternatives:

   • Calcineurin inhibitors: Pimecrolimus cream for eczematous conditions 3
   • Menthol-containing preparations: For temporary relief of itching 2
   • Capsaicin cream: Particularly for uremic pruritus 1

Second-line options:

1. Immunomodulating therapies:

   • Ciclosporin: Effective in about two-thirds of patients with severe autoimmune urticaria 1
   • Other immunosuppressants: Consider tacrolimus, mycophenolate mofetil for autoimmune urticaria 1
   • Azathioprine: For steroid-dependent pruritus 4

2. Phototherapy:

   • Narrow-band UVB: May be beneficial for pruritus associated with various conditions 1
   • BB-UVB or PUVA: For specific conditions like polycythemia vera 1

3. Other systemic medications:

   • Gabapentin: Particularly useful in elderly patients and uremic pruritus 1
   • Nifedipine: May reduce pruritus in chronic urticaria 1
   • Tranexamic acid: For idiopathic angioedema without weals 1

Special Situations

Elderly patients:

• Start with emollients and topical steroids for at least 2 weeks 1
• Use moisturizers with high lipid content 1
• Consider gabapentin if initial treatment fails 1
• Avoid sedating antihistamines 1

Severe or refractory cases:

• Consider referral to dermatology 1
• For autoimmune urticaria, consider plasmapheresis or intravenous immunoglobulins in severe cases 1

Common Pitfalls and Caveats

1. Misdiagnosis: Ensure proper diagnosis as some skin diseases can mimic others 5
2. Drug reactions: Always consider medication-induced rash, which may require discontinuation of the offending agent 6, 7
3. Inadequate treatment duration: Some conditions require longer treatment courses before improvement is seen
4. Overlooking psychological factors: Chronic pruritus can have significant psychological components 1
5. Inappropriate antihistamine use: Long-term use of sedative antihistamines may predispose to dementia 1

When to Refer to Secondary Care

Refer patients to a dermatologist or specialist when:

• There is diagnostic doubt
• Primary care management does not relieve symptoms
• The condition is severe or rapidly worsening
• There is suspicion of underlying malignancy or systemic disease 1

Remember that pruritus alone can rarely be the presenting feature of serious conditions such as bullous pemphigoid, particularly in the elderly, which may require specific investigations like skin biopsy 1.