Perforating Folliculitis: A Transepidermal Elimination Disorder

A 62-year-old male presented with complaints of dark, raised, pruritic lesions over bilateral upper and lower limbs for two months. The lesions initially started on the legs and were associated with pruritus and gradually progressed to involve the entire upper and lower limbs. The patient gave a 10-year history of uncontrolled diabetes, treated with oral hypoglycaemics and a 5-year history of chronic kidney disease. On examination, the patient exhibited multiple hyperpigmented papules and nodules over the bilateral upper and lower limbs [Table/Fig-1]. Based on the clinical presentation, the differential diagnoses considered were perforating folliculitis, Kyrle’s disease, acquired perforating collagenosis, prurigo nodularis and hypertrophic lichen planus. Upon investigating, the patient had a fasting blood glucose level of 320 mg/dL and a creatinine value of 2.5 mg/dL. Histopathological examination revealed dilated hair follicles filled with basophilic debris, collagen, keratin and neutrophils. Transepithelial extrusion of collagen into hair follicles, along with perifollicular inflammatory infiltrate composed of lymphocytes and neutrophils, was observed [Table/Fig-2]. Masson’s trichrome stain confirmed the presence of extruded collagen, supporting the diagnosis of perforating folliculitis [Table/Fig-3]. Management included optimisation of elevated creatinine levels and improved glycaemic control, alongside a 7-day course of tablet Doxycycline, tablet Bilastine and twice daily application of keratolytic-based emollient containing urea and lactic acid. The patient was subsequently lost to follow-up and further clinical progression could not be assessed.