Plantar warts (i.e., verruca pedis) are caused by infection of the epidermal skin layer with the human papillomavirus (HPV). Plantar warts were discussed as far back as the ancient Greeks and Romans. They were subsequently identified as being caused by infectious agents in the late 1800s. HPV, a member of the Papovaviridae family, was identified in 1949 and is composed of double-stranded DNA. The peak incidence of plantar warts occurs in the teenage years.1 They are estimated to occur in 10% of children and young adults, with a greater prevalence in females. HPV enters the host keratinocyte through an epidermal abrasion with the help of a transiently impaired immune system. It is found in the upper epidermis and results in squamous epithelial cell hyperplasia. Numerous types of HPV exist. Simple plantar warts are mainly due to HPV types 1, 2, 4, 27, or 57.
Two-thirds of untreated common warts in children regress spontaneously within 1 to 2 years.1,2 Patients seek treatment despite these high remission rates in part because of their location. Large warts on weight-bearing areas can be painful and disabling. They can be transmitted to adjacent or distant body areas if left untreated. Patients often present with the plantar wart and request its removal. No single therapy has been proven effective at achieving complete remission and there are many different approaches to therapy. Warts typically continue to increase in size and distribution and may become more resistant to treatment over time.3
This chapter summarizes the pathogenesis of plantar warts and three techniques for their removal. The Dermatologist has other treatments they can apply to remove plantar warts.4-6 This includes ablation, the injection of a variety of substances, laser removal, and needling.
ANATOMY AND PATHOPHYSIOLOGY
One must recall the layers of the skin to understand the pathogenesis of the HPV (Figure 221-1). The skin is composed of the epidermis, the dermis, and the subcutaneous tissue or hypodermis. The epidermis on the sole of the foot consists mainly of stratified squamous epithelium. The thickness of the epidermis ranges from 0.05 mm on the dorsal surface of the foot to 1.5 mm on the plantar surface.7 HPV replication occurs in the most superficial epidermal layer. The dermis is composed of connective tissue and serves as a scaffold for the skin. The blood vessels, nerves, glands, and hair follicles are in the dermis.
HPV is a DNA virus. It gains access to host cells and uses the host’s replicating cell proteins to manufacture viral proteins and DNA. This replication process induces epithelial cell hyperplasia and results in the mound of thickened skin observed in a plantar wart. The HPV remains in the epidermis but spreads laterally from ...