Zoon balanitis is a chronic, idiopathic, reactive balanoposthitis secondary to a dysfunctional foreskin, characterized by silent symptoms and florid signs. A similar clinical condition has been described in women and named vulvitis circumscripta plasmacellularis.
Zoon originally described this distinctive benign balanitis/balanoposthitis in 1952.
Etiology is still unclear. Researchers believe that it is due to irritation due to the retention of urine, smegma, and scale in the context of a dysfunctional foreskin. It does not occur in circumcised men. This retention occurs between 2 desquamative, secretory, hyper colonized epithelial surfaces under conditions of inadequate hygiene and repeated infection. Also, friction, heat, trauma, can be contributing factors. Professionals conclude that the 2 main trigger factors are, firstly, constant exposure to humidity, and secondly, constant exposure to chronic irritation. This explains why the Zoon balanitis lesions go through long remission after circumcision.
It is important to keep in mind that the foreskin may be dysfunctional due to a number of co-existing diseases including lichen sclerosus, chronic non-specific inflammation, and infection, lichen planus, psoriasis or eczema.
Other theories include chronic infection with Mycobacterium smegmatis or chronic infection with human papillomavirus (HPV). These theories have not been validated. Given that this condition does not occur in circumcised patients, it is reasonable to propose the hypothesis that the foreskin has a key role in its pathogenesis.
It is described as an infrequent entity; however, it is probably underreported or underdiagnosed. Mallon et al. reported 27 cases of Zoon balanitis among 357 patients with the genital disease. Pearce et al. reported 26 patients with 226 penile biopsies (10%). Kumar et al. reported a prevalence of 5.82%.
It can present at any age, but it is usually seen in elderly uncircumcised men. Unlike other some inflammatory penile dermatoses, it is generally not thought to be a precursor for neoplasia.
Long-lasting erythematous lesions involving the glans or prepuce may be difficult to classify, and biopsy is required to confirm the diagnosis and/or to rule out other conditions such as erythroplasia of Queyrat, fixed drug eruption, psoriasis, among others.
The histopathology in Zoon balanitis has a distinctive pattern, which consists of epidermal atrophy, lozenge keratinocytes with watery spongiosis and a dense lichenoid subepidermal infiltrate composed largely (more than 50%) of plasma cells. Erythrocyte extravasation and hemosiderin deposition are often noted, which corresponds to cayenne spots clinically observed.
It presents as symmetrical, well-marginated, erythematous, shiny plaques with multiple pinpoint redder spots, “cayenne pepper spots” involving the glans, prepuce, or both. Vegetative, erosive and “multiple” lesion variants have also been reported. Usually, the condition is asymptomatic, though pruritus may be present.
The course tends to be chronic and may persist for months to years, and sometimes poorly responsive to topical treatment.
Recently, dermoscopic findings in Zoon balanitis have been described in 11 patients, which include focused curved vessels (100%) in different shapes, including serpentine (100%), convoluted (45 % to 50%), chalice-shaped (27.3% to 25%); orange-brownish structureless areas (75% to 81%), linear irregular blurry vessels (36.4% to 37.5%) and dotted vessels (25% to 27.3%). These findings might assist the clinical diagnosis of Zoon balanitis, distinguishing it from its main differential diagnoses, such as erythroplasia of Queyrat, which shows scattered glomerular vessels; psoriasis, which displays regular dotted vessels and seborrheic dermatitis and non-specific balanoposthitis, usually showing linear irregular unspecific blurry vessels.
The use of reflectance confocal microscopy in differentiating between balanitis and carcinoma in situ has been evaluated. Balanitis shows a nucleated honeycomb pattern and vermicular vessels scattered small bright sells and round vessels, whereas carcinoma in situ shows an atypical honeycomb pattern, disarranged epidermal pattern, and round nucleated cells.
Clinicians should teach the patient adequate hygiene measures.
First-line therapy continues to be circumcision, which is the only therapy that provides long-term, full remission. Some patients often reject procedures in this sensitive area. Other options include topical steroids, calcineurin inhibitors, mupirocin, photodynamic and laser therapy, but the disease tends to relapse with the use of any of these treatments.
The use of topical steroids in the treatment of plasma cell balanitis has been used, although there is little evidence to support its use. Tang et al. reported a good response to a combination cream of oxytetracycline 3%, nystatin 100,000 units/g, and clobetasone butyrate 0.05% (Trimovate) until a complete clinical resolution was observed. Three of ten patients had recurrences within 3 months after cessation of therapy and responded to the second course of Trimovate cream. A fourth patient had three recurrences within 12 months, and each responded within a few days, and he continued on follow-up.
Calcineurin inhibitors, such as tacrolimus 0.1 and 0.3% and pimecrolimus 0.1% have been used, with complete remission after 3 to 8 weeks of therapy. However, there has been concern regarding a relationship between topical calcineurin inhibitors and carcinogenesis.
Photodynamic therapy has not yet been well established since it’s mostly based on case reports. Nevertheless, it has been considered a moderately effective and safe option for Zoon balanitis and has been used in refractory lesions.
Carbon dioxide and erbium:YAG lasers are alternatives that have shown variable outcomes. Erbium:YAG was used with a focus on mostly 3 mm. The frequency employed was 8 Hz, the impulse energy was mostly 800 mJ. In most patients, a complete re-epithelization was achieved within ten days. There was complete clearing of lesions during follow-up (3 to 30 months). There were no major complications, including phimosis. The erbium:YAG laser offers a precise superficial ablation with low thermal injury, low risk of scarring, low pain and rapid healing.
Mupirocin 2% ointment 3 times daily for 6 weeks to 3 months, has shown temporary complete resolution in two cases. This could be explained by the possibility that Zoon balanitis might be associated with bacterial colonization or super-antigen.
It includes candidiasis, contact dermatitis, fixed drug eruption, Kaposi’s sarcoma, herpes simplex virus, lichen planus, lichen sclerosus, pemphigus vulgaris, erythroplasia of Queyrat, psoriasis, secondary syphilis, and squamous cell carcinoma.
Co-infection with Candida may occur frequently.
Zoon balanitis is considered a benign entity, although isolated cases have been found in association with squamous cell carcinoma. In 1999, a case of penile carcinoma arising in a patient with Zoon balanitis was described by Joshi. In 2001, Bunker claimed that there were zoonoid changes in clinical and histological features in some cases of lichen sclerosus, lichen planus, Bowenoid papulosis, and penile cancer. These zoonoid changes could suggest that Zoon balanitis could be a premalignant condition. Further studies are necessary to establish this association.