Introduction: Hyperkeratotic follicular spicules have been associated with a variety of conditions. Propionibacterium acnes, a commensal commonly encountered in hair follicles, have not previously been linked pathogenically to the formation of such follicular spicules.
Case report: A 22-year-old Chinese man presented with multiple filiform, follicular white spicules over his neck, upper chest and upper back for 6 years. Skin biopsy of a neck spicule revealed an elongated, hyperkarotic follicular plug with clumps of bacilli staining positively for gram stain and giemsa stain. Hair follicle was normal. Anaerobic culture of the spicules grew Propionibacterium acnes. He was otherwise well with no serum paraproteinaemia. He was treated with 4% erythromycin gel on the left side of his neck and 5% urea cream on the right side for one month. The side treated with the erythromycin gel showed a significant reduction in the number of hyperkeratotic spicules, with minimal difference to the opposite side. Oral erythromycin resulted in clearance of the body and neck lesions, with recurrence when erythromycin was stopped.
Conclusion: The presence of abundant P acnes within the follicular plug, prompt resolution of these spicules with treatment against P acnes (erythromycin), and recurrence of the lesions upon stopping treatment, supports the view that P acnes is pathogenic in this condition.