Phenobarbital

A 27-year-old woman developed atypical drug-induced hypersensitivity syndrome (DIHS) with progressive hair loss after taking phenobarbital. She initially presented with a confluent erythematous maculopapular rash and severe facial edema. Treatment with prednisolone controlled her acute symptoms, but tapering off the drug over 6 months led to skin eruptions and hair loss. Although her skin lesions were resolved with steroids, her alopecia worsened. A biopsy revealed an increase in telogen hair follicles, suggesting acute telogen effluvium, and lymphocytic cell infiltration around the arrector pili muscle insertion point, exocytosis, and liquefaction degeneration were also noted. Her hair loss persisted for 2 weeks, followed by regrowth and recovery of hair density over 2 months. The case highlighted an immune response involving the bulge region of hair follicles in addition to telogen conversion as contributing factors to her hair loss.