Penile papulonecrotic tuberculid in a 30-year-old male: A rare manifestation of cutaneous tuberculosis

INTRODUCTION

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is a major public health issue in developing countries. While pulmonary TB is the most common form, extrapulmonary TB accounts for a significant proportion of total cases. Cutaneous TB is a rare manifestation, comprising <2% of all TB cases, and is further categorized into true cutaneous TB and tuberculids. Tuberculids are considered hypersensitivity reactions to hematogenously disseminated bacilli or their antigens and occur in individuals with a moderate to high degree of immunity.

Papulonecrotic tuberculid (PNT) is one of the three main types of tuberculids, alongside lichen scrofulosorum and erythema induratum. PNT usually presents as recurrent crops of symmetrically distributed, necrotizing papules on the extensor surfaces of limbs, buttocks, or trunk. Genital involvement is rare and can pose a diagnostic challenge, often being mistaken for sexually transmitted infections (STIs), vasculitis, or other inflammatory dermatoses. We present a rare case of penile PNT in an otherwise healthy young male with no systemic symptoms of TB.

CASE REPORT

A 30-year-old heterosexual, married male presented to our dermatology clinic with multiple painless ulcerative lesions over the glans penis, persisting for the past 8 months [Figure 1]. He shared that he had visited several dermatologists and tertiary care centers during this time, where he was treated empirically for conditions such as genital ulcer disease and herpes and had undergone multiple blood tests, all of which were inconclusive. The patient recalled that the lesions initially started as small, red, raised papules which gradually developed central necrosis followed by crusting, with no associated pain, discharge, or systemic symptoms. There was no associated itching, burning, bleeding, or urethral discharge. The patient reported no history of fever, weight loss, night sweats, cough, or other constitutional symptoms. He denied extramarital sexual exposure. No similar lesions were present elsewhere on the body.

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Figure 1:

Ulcerative lesions over the glans penis.

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His medical and surgical histories were unremarkable. There was no known history of TB or recent contact with TB patients.

Cutaneous examination revealed multiple discrete necrotic papules with central crusting, distributed over the dorsal aspect of the glans penis. On examination, there were multiple firm, tender, mildly indurated, punched-out ulcers with irregular margins, and yellowish white necrotic slough on the floor, varying in size from 1 cm to 0.5 cm. No lymphadenopathy was noted in the inguinal region. There were no oral or skin lesions elsewhere. Systemic examination was within normal limits.

A skin biopsy from one of the penile lesions showed wedge-shaped necrosis in the dermis, leukocytoclastic vasculitis, granulomatous infiltration around blood vessels, and occasional Langhans’ giant cells [Figures 2 and 3].

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Figure 2:

Close up of casseation necrosis with pyknotic neutrophils within. (Hematoxylin and eosin stain, 400x).

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Figure 3:

Image showing ill defined granuloma with lymphohistiocytic peripheral infiltrate and central casseation necrosis, overlying ulceration. (Hematoxylin and eosin, 100x).

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Ziehl–Neelsen staining for acid–fast bacilli (AFB) was negative. The patient was further investigated for the Mantoux test.

A Mantoux test using 5 tuberculin units (TU) of purified protein derivative was performed and showed an induration of 19 mm at 48 h, indicating a strong tuberculin sensitivity. Routine investigations, including complete blood count, erythrocyte sedimentation rate, blood sugar levels, and liver and renal function tests, were within normal limits. Serological tests for human immunodeficiency virus, hepatitis B and C, and venereal disease research laboratory were all negative. Chest X-ray was unremarkable.

Given the typical clinical presentation, a strongly positive Mantoux test, histopathology suggestive of PNT, and absence of systemic or localized focus of active TB, a diagnosis of penile PNT was made.

The patient was initiated on standard Category I anti-tubercular therapy (ATT): isoniazid (H), rifampicin (R), pyrazinamide (Z), and ethambutol (E) for the intensive phase of 2 months, followed by H and R for a continuation phase of 4 months. Within 4 weeks, the lesions showed significant healing with crust resolution and flattening. Complete clinical resolution occurred by the end of the intensive phase, and no recurrence was seen at the 4-month follow-up [Figure 4].

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Figure 4:

Resolution of lesions by the end of the intensive phase, at the 4-month follow-up.

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DISCUSSION

PNT is a rare manifestation of cutaneous TB characterized by recurrent crops of necrotizing papules that may ulcerate and heal with varioliform scarring. The condition is considered an immunological reaction to mycobacterial antigens in patients with a relatively competent immune system. While the classical sites of involvement are the extensor surfaces of the extremities, involvement of the genitalia, especially the penis, is exceedingly rare, with only a handful of cases reported in the literature.

The exact pathogenesis involves a delayed-type hypersensitivity response to TB antigens disseminated through the bloodstream from a latent or past focus of infection. Importantly, the lesions are paucibacillary or even bacilli, and AFB is usually not demonstrable in tissue, making microbiological confirmation difficult. Therefore, diagnosis rests on a constellation of clinical, histopathological, and immunological findings along with the exclusion of other conditions.

A strongly positive tuberculin skin test (in this case, 19 mm induration) supports the diagnosis, as does a prompt response to ATT. Histopathology typically reveals necrotizing granulomatous inflammation with vasculitis, consistent with our findings.

Genital involvement by PNT is exceptionally rare. Kumar et al. described a similar case of PNT localized to the penis, underlining the diagnostic dilemma posed by such atypical presentations.^[1] Another report by Gangalakshmi and Sankaramahalingam described TB of the glans penis as a rare presentation, further supporting that even isolated penile lesions can be a manifestation of TB, despite the absence of systemic disease.^[2]

The main differential diagnoses of necrotic papular lesions on the penis include [Table 1]:

In our patient, the lack of constitutional symptoms, no systemic focus of TB, a strong Mantoux reaction, negative sexually transmitted disease (STD) workup, supportive histopathology, and complete resolution with ATT clinched the diagnosis of PNT.

This case emphasizes the importance of considering cutaneous TB in the differential diagnosis of unusual penile lesions, especially in endemic regions. Failure to recognize this condition can lead to unnecessary investigations, anxiety over STIs, and delayed treatment.

CONCLUSION

Papulonecrotic tuberculid (PNT) of the penis is an extremely rare presentation of cutaneous tuberculosis that can mimic a variety of infectious and non-infectious genital dermatoses. Recognition of this entity requires a high index of suspicion, especially in tuberculosis-endemic areas. Diagnosis is primarily clinicopathological, supported by a strongly positive tuberculin skin test and characteristic histological features, even in the absence of demonstrable acid-fast bacilli. A favorable therapeutic response to anti-tubercular therapy further reinforces the diagnosis. This case highlights the need for dermatologists and clinicians to include tuberculids in the differential diagnosis of chronic, necrotic penile papules or ulcers, as timely identification and appropriate treatment can prevent misdiagnosis, reduce patient distress, and ensure complete resolution of lesions.