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Am Fam Physician. 2008;78(9):1081-1082

Author disclosure: Nothing to disclose.

An otherwise healthy 61-year-old man presented with a persistent rash on his penis. He said that the lesion may have slightly increased in size over the previous six months. He had no history of atopic dermatitis, psoriasis, lichen planus, or sexually transmitted diseases. The patient noted episodic tenderness. Previous use of low-potency topical corticosteroids did not alter the appearance of the rash.

On physical examination, a well-demarcated, pink-to-red plaque was noted on the distal penile shaft and coronal rim. Histopathologic examination revealed epidermal thinning, spongiosis, and a dense subepidermal infiltrate composed of plasma cells and neutrophils.

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Question

Based on the patient's history and physical examination, which one of the following is the most likely diagnosis?

Discussion

The answer is E: Zoon balanitis. Zoon balanitis, also known as balanitis circumscripta plasmacellularis or plasma cell balanitis, is an uncommon, benign, idiopathic, inflammatory penile dermatosis. The condition was first described in 1952 by J.J. Zoon.1 Zoon balanitis usually involves the glans penis and the prepuce, but it can occur on the balanopreputial fold and internal surface of the foreskin.2,3 It primarily occurs in middle-age or older men who are uncircumcised and presents on the dorsal surface of the penis, where more trauma tends to occur. This is also the site where maximal friction occurs during foreskin retraction. Numerous factors are thought to be involved in its etiology, including moisture, friction, repeated infections, and poor hygiene.2,4 Exposure of the mucosa to chronic irritation and a humid environment explains why Zoon balanitis is less common in circumcised men.2

Clinically, Zoon balanitis appears as a sharply demarcated, bright-red patch on the glans penis, coronal sulcus, or inner prepuce surface with frequent erosion and bleeding.4 Other features include pinpoint purpuric spotting and yellow discharge. Lesions are usually present for two to three years before diagnosis. Symptoms often include pruritus, burning, and tenderness.

Key histologic features of Zoon balanitis include epidermal thinning, possibly with some superficial erosion. Plasma cells and band-like infiltrates are present in the superficial dermis. Dilated capillaries and extravasated erythrocytes may also be present.2 More advanced lesions may include fibrosis and hemosiderin deposits in the upper dermis, as well as atrophy or complete loss of the overlying epidermis.4 Telangiectasia may occur in the inflammatory infiltrate. Suggested pathogenesis is a result of constant friction or trauma of the barely keratinized skin of the glans penis and inner prepuce surface in a moist environment. Compared with other areas, these regions of the penis are less resistant to mechanical forces. Irritation from moisture, friction, or external contacts and normal colonizing organisms that become pathogenic may be contributory.5

Prevention involves good personal hygiene and avoidance of potential irritants. Circumcision is the most effective long-term treatment because it reduces common infective penile dermatoses.6 Topical tacrolimus 0.1% ointment (Protopic), applied twice daily, has proved to be safe and effective.3 Other topical agents, such as antibacterials, corticosteroids, and antifungals, have had limited success and are not curative.2 Laser ablation (e.g., carbondioxide or erbium: YAG laser) has been an effective alternative to circumcision.2 Topical imiquimod 5% cream (Aldara) has recently been used successfully.7

ConditionCharacteristics
Balanitis xerotica obliteransPruritic lesion on the genitals; may be treated with topical therapy; atrophic white patches or plaques on the glans penis and prepuce
Candidal balanitisDiagnosed via potassium hydroxide testing to detect yeast; topical treatment is effective; erythema of the glans penis or foreskin
Erythroplasia of QueyratPrecancerous lesion diagnosed with biopsy
SyphilisNonpainful lesion on the genitals with corresponding patient history
Zoon balanitisInflammatory penile dermatosis; often responds to topical therapy

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This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

A collection of Photo Quiz published in AFP is available at https://www.aafp.org/afp/photoquiz

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