Arsenical keratoderma

Specialty: Skin.

• arsenical hyperkeratosis
• multiple arsenical keratoses

Why it occurs

• Chronic systemic exposure to inorganic arsenic through prolonged consumption of contaminated well water (chronic regional endemic hydroarsenicism - HACRE)
• Occupational exposure in pesticide manufacturing, copper smelting, or mining without adequate protective equipment
• Historical therapeutic use of arsenic-rich solutions (such as Fowler's solution) for the treatment of psoriasis or asthma in the past
• Accidental or intentional ingestion of industrial chemical compounds with arsenic
• Cumulative chromosomal alteration and cellular interference with epidermal DNA repair mechanisms.

Initial workup

Measurement of arsenic in 24-hour urine (indicator of recent exposure) and quantification of arsenic in hair or nails (sensitive indicator of long-term chronic accumulation). Punch skin biopsy of suspicious keratotic papules to evaluate cellular atypia, dyskeratosis and rule out squamous cell carcinoma in situ. Systemic screening tests including chest x-ray and urinary cytology.

Standard management

• Acitretin — systemic retinoid of choice to prevent and control aberrant cellular keratinization and reduce the rate of progression to skin carcinomas, doses of 10 to 25 mg daily orally under close medical supervision
• 5-Fluorouracil 5% Cream — topical chemotherapy applied to individual lesions to induce their selective regression
• Imiquimod 5% cream — local immune modulator useful in keratosis with suspected focal atypia
• 10% salicylic acid ointment (supportive keratolytic to reduce the thickness of hard plaques).