What are the likely causes and appropriate management for severe left‑hand pain and pruritus in a 79‑year‑old woman with hyperlipidemia, osteoporosis, bilateral carpal tunnel syndrome, fibromyalgia, and iron‑deficiency anemia?

Severe Left Hand Pain and Pruritus in a 79-Year-Old Woman

The most likely cause of this patient's severe left hand pain and itchiness is her known iron deficiency anemia, which accounts for 25% of all pruritus cases with underlying systemic disease and can cause complete cessation of symptoms shortly after starting iron replacement therapy. 1, 2

Primary Diagnostic Consideration: Iron Deficiency Anemia

Iron deficiency anemia is the single most common systemic cause of generalized pruritus and should be your first target for investigation and treatment in this patient. 1, 2

• Iron replacement therapy leads to complete cessation of pruritus very shortly after commencement in many cases 1
• The British Association of Dermatologists specifically identifies iron deficiency as causing 25% of all pruritus cases with systemic disease 1, 2
• Given her documented iron deficiency anemia, this is the most treatable and likely explanation for her itchiness 2

Immediate Diagnostic Workup

Check full blood count, ferritin levels, serum iron, and total iron binding capacity immediately. 1

• Ferritin is an acute-phase protein and may be falsely elevated despite true iron deficiency 1, 3
• If ferritin appears "normal" but iron deficiency is suspected, serum iron and total iron binding capacity must be checked 1
• A trial of iron replacement should be given if ferritin is below 15-25 µg/L or if there is anemia or microcytosis 1

Differential Diagnosis for Localized Hand Pain

While the pruritus is likely systemic from iron deficiency, the severe localized left hand pain requires separate consideration of her bilateral carpal tunnel syndrome. 4, 5

• Her known bilateral carpal tunnel syndrome can cause severe pain in the distribution of the median nerve (thumb, index, middle fingers, and radial half of ring finger) 4
• Carpal tunnel syndrome is the most common entrapment neuropathy and affects mainly middle-aged women 5
• The association between carpal tunnel syndrome and rheumatic diseases exists, though fibromyalgia is not typically a direct cause 6

Other Systemic Causes to Exclude

While iron deficiency is most likely, briefly evaluate for other causes of generalized pruritus in the elderly. 1

• Pruritus in the elderly (Willan's itch) is very common in those over 65 years and may be associated with xerosis (dry skin) 1
• Polycythemia vera causes aquagenic pruritus (triggered by water) and should be considered if symptoms worsen with bathing 1
• Hematological causes account for approximately 2% of generalized pruritus cases 1
• Bullous pemphigoid can rarely present with pruritus alone in the elderly before skin lesions appear 1

Immediate Management Algorithm

Step 1: Treat the Iron Deficiency

Start iron replacement therapy immediately if ferritin is low or iron studies confirm deficiency. 1

• Oral ferrous preparations at 3-6 mg/kg elemental iron per day are first-line 7
• Expect improvement in pruritus within days to weeks of starting therapy 1

Step 2: Symptomatic Relief for Pruritus

While awaiting iron replacement effects, provide symptomatic management. 1

• Apply emollients liberally and frequently, preferably high lipid content moisturizers 1
• Consider topical steroids for at least 2 weeks to treat any asteatotic eczema 1
• Trial of non-sedating antihistamine for short course 1
• Avoid sedating antihistamines in this 79-year-old patient 1
• Consider gabapentin if initial measures fail, as it may benefit elderly patients with pruritus 1

Step 3: Address Carpal Tunnel Syndrome

If severe localized hand pain persists despite treating systemic causes, reassess carpal tunnel syndrome severity. 4, 5

• Conservative management includes splinting, local corticosteroid injection, or physical therapy for mild to moderate cases 4
• Local corticosteroid injection can provide relief for more than one month 4
• Surgical decompression should be offered if symptoms have not improved after 4-6 months of conservative therapy or if severe 4
• Obtain electrodiagnostic studies to determine severity and surgical prognosis if surgery is planned 4

Critical Pitfalls to Avoid

Do not assume the pruritus is simply "elderly skin" without checking iron studies. 1, 2

• Iron deficiency is highly treatable and reversible 1
• Missing this diagnosis condemns the patient to unnecessary suffering 2

Do not use sedating antihistamines long-term in this elderly patient. 1, 2

• Sedating antihistamines should not be used in elderly patients with pruritus due to potential dementia risk 1

Do not attribute all symptoms to fibromyalgia without objective evaluation. 4, 5

• Fibromyalgia can cause widespread pain but does not explain localized severe hand pain with objective findings 4
• Carpal tunnel syndrome requires specific evaluation and treatment 4, 5

When to Refer

Refer to secondary care if diagnostic doubt exists, symptoms persist despite iron replacement after 4-6 weeks, or the patient remains distressed despite primary care management. 1

• Consider dermatology referral if pruritus does not respond to iron replacement 1
• Consider orthopedic or hand surgery referral if carpal tunnel symptoms are severe or refractory to conservative management 4