Porokeratosis of Mibelli
Overview
Porokeratosis of Mibelli: A rare skin disorder characterized by skin lesions that tend to spread and may be located on the limbs, face, genitals and mouth. The condition progresses and regresses spontaneously and mild scarring may result. There is an associated increased risk of skin cancer.
Symptoms
The list of signs and symptoms mentioned in various sources for Porokeratosis of Mibelli includes the 4 symptoms listed below: * Miliar translucent skin bumps * Dark centered small skin bumps * Single skin bumps * Groups of small skin bumps Note that Porokeratosis of Mibelli symptoms usually refers to various symptoms known to a patient, but the phrase Porokeratosis of Mibelli signs may refer to those signs only noticable by a doctor.
Causes
Risk factors for porokeratosis include genetic inheritance, ultraviolet light exposure, and immunosuppression. One study found that approximately 10% of patients who had undergone renal transplantation developed porokeratosis. * Classic porokeratosis (Mibelli) - Autosomal dominant inheritance and immunosuppression are the usual causes. - PM has been seen following radiation therapy, at burn wounds, and at hemodialysis sites.
Diagnosis
In cases of diffuse thickening of the skin, a thyroid profile with T 3 , T 4 , and TSH should be done. This should also identify hypothyroidism. A positive ANA test with a speckled pattern will help identify scleroderma , but a skin biopsy should also be done. An antisclerodermal antibody titer is also useful if available. Esophageal motility studies will be helpful in early diagnosis. A skin biopsy will help identify many of the other conditions mentioned above. Urine for porphyrins will help identify porphyria.
Treatment
The approach to treatment must be individualized, based on the size of the lesion and the anatomical location, the functional and aesthetic considerations, the risk of malignancy, and the patient's preference. Protection from the sun, use of emollients, and watchful observation for signs of malignant degeneration may be all that is needed for many patients. If lesions are widespread and medical treatment is desired, several medications have potential benefit. * Topical 5-fluorouracil: Topical 5-fluorouracil can induce remission in all forms of porokeratosis. Treatment must be continued until a brisk inflammatory reaction is obtained. Enhancement of penetration, which heightens the response, may be achieved by occlusion or the addition of topical tretinoin. Concurrent use of topical steroids may ease discomfort without reducing long-term improvement. Recurrences may be seen. * Topical vitamin D-3 analogues: Both calcipotriol and tacalcitol have been shown to be effective after 3-6 months of treatment of DSAP. * Topical imiquimod 5% cream: This has been shown to be effective for treating PM. * Oral retinoids (isotretinoin, etretinate, and acitretin): The use of oral retinoids in patients who are immunosuppressed, who are at higher risk for malignant degeneration, may reduce the risk of carcinoma in porokeratotic lesions. o Oral isotretinoin at 20 mg daily combined with topical 5-fluorouracil is reported to be effective for DSAP and PPPD, but it causes burning, itching, and painful erosions. o Reports of etretinate efficacy are conflicting. Etretinate at doses of 75 mg/d for 1 week followed by 50 mg/d has been shown to be helpful in linear porokeratosis and symptomatic PM. Higher doses of 1 mg/kg/d were reported to exacerbate lesions of DSAP after 4-6 weeks of treatment. Even when etretinate therapy is successful, relapses may occur. Digitate keratoses were reported to develop after the use of etretinate for DSAP. o Acitretin, a second-generation monoaromatic retinoid that is the active metabolite of etretinate, is likely to have results similar to those of etretinate. However, no studies have reported the effect of acitretin on porokeratosis.