Penile granuloma annulare: An uncommon entity

INTRODUCTION

Granuloma annulare (GA) is an uncommon benign, granulomatous inflammatory cutaneous lesion that has no proven etiology and is often self-resolving. It usually involves the hands and feet, commonly in young females.^[1-3] It is associated with diabetes mellitus, thyroid disease, mild trauma, hyperlipidemia, infections (Epstein–Barr virus, human immunodeficiency virus, varicella-zoster virus, and tuberculosis), vaccines, malignancy, and certain drugs (tumor necrosis factor [TNF]-alpha inhibitors).^[4] Very few cases of penile GA have been reported.

CASE REPORT

A 50-year-old healthy male presented with asymptomatic raised lesions over the glans for 1 year. There were no other genitourinary complaints or any history suggestive of high-risk sexual behavior. On examination, there were multiple skin-colored firm and smooth papules which were coalescing to form plaques over the glans penis [Figures 1 and 2]. The papules were non-tender and the overlying skin was intact. There was no inguinal or femoral lymphadenopathy. Our differential diagnosis was genital warts, lichen planus, GA, and sarcoidosis. Routine hematological and biochemical tests were normal. Human immunodeficiency virus, hepatitis B, hepatitis C, syphilis serology including Venereal Disease Research Laboratory, and treponema pallidum hemagglutination were negative. Angiotensin-converting enzyme levels were normal.

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Figure 1:

(a and b) Clinical image showing multiple skin-colored papules coalescing to form plaque.

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Figure 2:

(a) The histopathology section showing granulomatous changes around degenerated collagen (Hematoxylin and Eosin stain ×10). (b) The histopathology section showing necrobiotic collagen with palisade of histiocyte surrounding it (Hematoxylin and Eosin stain ×40).

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A biopsy from the papule, under scanner showed a granulomatous reaction involving the whole of the dermis. On higher magnification, there was interstitial infiltrate of histiocytes with a central core of necrobiotic collagen [Figures 2a and b] consistent with interstitial GA. The patient was treated with mometasone 0.05% cream bd for 15 days and was switched to tacrolimus 0.03% ointment with little improvement, and there was persistent induration. Pentoxifylline 400 mg thrice daily was added for 1 month which showed a marked response in the form of a decrease in the induration of the lesion.

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Figure 3:

Post-treatment clinical image showing the resolution of papules and plaques over the glans.

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DISCUSSION

GA is a necrobiotic disorder of unknown etiology. It is often seen over acral sites such as the dorsum of hands, elbows, and feet and involvement of the penis is rare.^[5-8] There are different types of GA, they are – annular (localized), generalized (disseminated), nodular (subcutaneous), and perforating forms. Histopathology of GA shows a palisade of histiocytes around a focus of necrobiosis, increased mucin deposition, and multinucleated giant cells. Clinically, the differential diagnosis includes sexually transmitted diseases, benign neoplasms, annular lichen planus, and psoriasis. Very few cases of penile GA have been reported and lesions restricted to the glans penis are even less. Treatment modalities include surgical excision, intralesional corticosteroids,^[9] topical tacrolimus, carbon-dioxide laser treatment,^[10] low-dose intralesional injections of recombinant human interferon-gamma,^[11] and pentoxifylline. The mechanism of action of pentoxifylline in GA is not known, but it is postulated that it has TNF-alpha blocking action, inhibition of macrophage activation, and hence granulomatous inflammation. It also reduces the blood viscosity and hence increases oxygenation.^[12] Penile GA seldom shows spontaneous resolution, unlike other forms.^[9]

CONCLUSION

Penile GA although rare should be considered in the differential diagnosis of granulomatous lesions of the penis and histological examination is crucial for its diagnosis to avoid over-treatment. We report this case for an uncommon presentation of GA at an unusual site.