Patchy alopecia in the central posterior occipital region

A woman in her 40s presented to the dermatology clinic with hair loss localised to the central posterior occipital region. One month previously she had undergone head and facial surgery for four hours, followed by sedation in the intensive care unit for 18 hours. Two days after surgery, she developed a scalp haematoma, followed by hair loss one week later. The patient had no history of trauma or exposure to specific harmful substances. Test results for thyroid function were unremarkable, and fungal test results were negative. On physical examination, a well defined bald patch measuring 6 cm×2 cm was observed in the central posterior occipital region (fig 1). Hair follicle openings were visible on trichoscopy, as well as follicular keratinous plugs, capillary dilation, and the emergence of short, fine new hairs, along with broken hair shafts (fig 2). A punch skin biopsy sample showed that most of the deep dermal hair follicles were in the telogen phase, and inflammatory cell infiltration was minimal (fig 3).