Dermatology · Viral Dermatoses
The facts most likely to be tested
Verrucae are caused by the Human Papillomavirus (HPV), a double-stranded DNA virus that infects the keratinocytes of the skin and mucous membranes.
The classic clinical presentation of verruca vulgaris (common wart) is a hyperkeratotic, exophytic papule with a verrucous (rough) surface.
A pathognomonic finding of common warts is the presence of thrombosed capillary loops, which appear as black dots on the surface of the lesion when pared down.
Verrucae plantares (plantar warts) are characterized by inward growth due to pressure, often causing pain with ambulation and obscuring normal dermatoglyphics (skin lines).
Condyloma acuminatum (anogenital warts) are typically caused by low-risk HPV types 6 and 11 and present as flesh-colored, cauliflower-like lesions.
First-line treatment for most cutaneous warts is topical salicylic acid or cryotherapy with liquid nitrogen to induce controlled tissue destruction.
Diagnosis of verrucae is primarily clinical, but a shave biopsy is indicated if the lesion is atypical, rapidly changing, or fails to respond to standard therapy to rule out squamous cell carcinoma.
Vignette unlocked
A 22-year-old male presents to the clinic complaining of a persistent, painful lesion on the sole of his right foot. On physical examination, there is a 1-cm hyperkeratotic papule that disrupts the normal dermatoglyphics of the skin. Upon paring the surface of the lesion with a scalpel, multiple black dots representing thrombosed capillary loops are visualized. The patient denies any history of immunosuppression or recent travel.
What is the most likely diagnosis?
Verruca plantaris (Plantar wart)
The vignette describes the classic clinical features of a plantar wart, specifically the disruption of dermatoglyphics and the presence of thrombosed capillary loops, which are pathognomonic for HPV-induced verrucae.
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High yield triage
Etiology / Epidemiology
Caused by HPV (Human Papillomavirus); transmitted via direct skin-to-skin contact or fomites.
Clinical Manifestations
Hyperkeratotic papules with thrombosed capillaries (black dots) and Auspitz sign absence.
Diagnosis
Primarily clinical diagnosis; biopsy reserved for atypical lesions to rule out malignancy.
Treatment
Salicylic acid or cryotherapy are first-line; avoid cryotherapy on face/genitalia.
Prognosis
Most resolve spontaneously within 2 years; recurrence is common.
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Epidemiology & Etiology
Verrucae are caused by various strains of HPV, a double-stranded DNA virus. Transmission occurs through direct contact or autoinoculation, often facilitated by skin trauma or maceration. Prevalence is highest in school-aged children and individuals with cell-mediated immunodeficiency.
Pertinent Anatomy
Lesions involve the epidermis, specifically the stratum spinosum and stratum corneum. Plantar warts (verruca plantaris) grow inward due to pressure, often causing pain with ambulation.
Pathophysiology
HPV infects basal keratinocytes, leading to hyperproliferation and hyperkeratosis. The virus induces koilocytosis, characterized by perinuclear cytoplasmic vacuolization. The characteristic black dots represent thrombosed capillaries within the papillary dermis.
Clinical Manifestations
Lesions present as rough, hyperkeratotic papules. Verruca vulgaris (common wart) is most frequent on hands; verruca plantaris on soles; verruca plana (flat wart) on face/legs. Thrombosed capillaries are pathognomonic. Red flags include rapid growth, bleeding, or ulceration, which necessitate biopsy to rule out squamous cell carcinoma.
Diagnosis
Diagnosis is clinical based on morphology. If the diagnosis is uncertain or the lesion is recalcitrant, a shave biopsy is the gold standard. Histology reveals koilocytes and papillomatosis.
Treatment
Salicylic acid (topical) or cryotherapy (liquid nitrogen) are first-line. For recalcitrant cases, consider intralesional immunotherapy or laser therapy. Cryotherapy is contraindicated in patients with peripheral vascular disease or neuropathy due to risk of tissue necrosis.
Prognosis
Spontaneous resolution occurs in 65% of cases within two years. Recurrence is frequent due to latent viral presence. Immunocompromised patients have significantly higher rates of treatment failure.
Differential Diagnosis
Corns/Calluses: lack thrombosed capillaries
Seborrheic Keratosis: 'stuck-on' appearance
Squamous Cell Carcinoma: ulcerated, non-healing
Molluscum Contagiosum: central umbilication
Condyloma Acuminatum: genital location