Flat warts, benign growths on the skin caused by human papilloma virus (HPV), could prove difficult to get rid of in many patients.
There are more than 100 types of HPVs, out of which 3, 10, 28 and 49 are most commonly associated with flat warts.
Flat warts, also called plane warts or verruca plana, are 1–4 mm in size, slightly raised above the skin surface, and, as the name denotes, flat topped. Flat warts are smooth and usually light brown, grayish yellow, grey or skin colored in appearance. Most of the time, flat warts are multiple and occur more frequently on the face, hands and lower legs.
Flat warts show new lesions along scratch marks or lines of injury on the skin, the well-known Koebner phenomenon.
Incorrect self treatment with topical steroids can cause extensive spread of the plane warts due to suppression of local immunity against the HPV.
Are Flat Warts Dangerous?
As a rule, flat warts are harmless and self limiting. At times, though, the HPV types causing flat warts can also cause widespread persistent eruptions, known as the epidermodysplasia verruciformis (EV). EV usually presents in childhood and is very resistant to treatment. Even after removal, flat warts in EV often recur, implying a defective immune response against the virus.
In rare instances, flat warts caused by HPV type 10 may result in cancer of the cervix and vulva in females. EV caused by HPV types 5, 8 and 9 may also culminate as skin cancers in later life.
Which are the Other Skin Diseases that May Resemble Flat Warts?
On the face, perioral dermatitis, syringoma, early lesions of adenoma sebaceum, flat seborrheic keratosis, actinic Keratosis and trichoepitheliomas may resemble flat warts.
On the hands, acrokeratosis verruciformis, lichen planus, stucco keratosis and seborrheic keratosis also have to be ruled out before making a diagnosis of plane warts.
On the body and extremities, generalized plane warts may resemble epidermodysplasia verruciformis, pityriasis versicolor, superficial actinic porokeratosis and seborrheic keratosis.
How to Get Rid of Flat Warts
Not all patients with flat warts require treatment, as the warts may resolve spontaneously over a few months in most patients. Treatment is usually advised for cosmetic reasons and when there is extensive spread of warts over the face and the extremities.
The management of plane warts depends on many factors like the extent and duration of lesions; site of involvement and the patient’s immunologic status. The treatment is different for different types of warts like the palmoplantar warts and genital warts.
Following are the common treatments available for plane warts:
- Imiquimod 5% cream is the most effective topical treatment for plane warts. It is applied 3 or 4 times weekly for 6–8 weeks. Imiquimod works by inducing immunological response against the human papilloma viruses. It can cause local irritation in some individuals.
- Topical retinoids, 0.05–0.1% strengths, applied twice a day for 4–8 weeks clear most flat warts.
- Topical application of benzoyl peroxide 10%, twice a day for 4–8 weeks is also effective in some cases.
- A 5% solution of 5-fluorouracil applied daily for a month is useful in getting rid of resistant plane warts.
- For those with a limited number of flat warts, cryotherapy, electrocautery and radiofrequency cautery are also effective. These have the potential of causing scars and should be reserved as final options in very resistant cases.
- Immunotherapy with dinitrochlorobenzene (DNCB) and interferon have also been tried in resistant cases with varying degree of success.
- Hypno-suggestion therapy was found to be effective in clearing plane warts in some anecdotal cases, especially in children.
To sum up, plane warts caused by human papilloma virus is a common, usually benign, condition which may require therapeutic intervention in some individuals.