Labial swelling: a rare presentation of pubic bone tuberculosis

Introduction

Tuberculosis (TB) presenting in the pubic bone is rare. Only 40 cases of pubic bone TB were identified by Hitesh et al. ¹ and its presentation as a labial swelling has not previously been reported.

Case report

A 25-year-old woman, married for 6 months, nulligravid, not using any contraception, presented with a right-sided labial swelling, noticed for one week. She also complained of a dull suprapubic ache for the previous month. There was no history of trauma, fever, weight loss, anorexia, infection, discharge or surgical intervention. There were no associated intestinal or urinary complaints. There was no history of tuberculous contact. The menstrual history was unremarkable. The past medical and family history was non-contributory.

On local examination, there was a single labial swelling, 4 × 3 cm in size, noted on the right anterior third which was non-tender, and not obviously inflamed (Figure 1). The skin overlying the swelling was normal, and no punctum nor sinus noted, with no regional lymphadenopathy. No cough impulse was exhibited. Vaginal and cervical examination was unremarkable with no obvious extension of the swelling or presence of a cyst. Systemic examination showed no abnormality. Serological tests for HIV, hepatitis and syphilis were negative. Ultrasonographic examination confirmed the swelling to be cystic. Fine needle aspiration cytology (FNAC) (Figures 3 and 4) showed epithelioid cell clusters admixed with histiocytes in a background of caseous necrosis suggestive of TB. Culture of the fluid sample confirmed the diagnosis of TB. Owing to the unusual site and presentation of the swelling, magnetic resonance imaging (MRI) was procured. This showed destruction of both pubic bones involving the pubic symphysis associated with a soft-tissue collection entering inferiorly into the right labium majus, suggestive of TB. After one week of commencement of anti-tubercular treatment (ATT), the cold abscess burst at home but this was not reported immediately by the patient. However, the lesion resolved completely after some months (Figure 2). A second MRI was performed to assess the response to ATT on account of the rarity of the site of the lesion and an increase in incidence of multi-resistant TB in our area. OPEN IN VIEWER

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Figure 2.

(a, b) Histopathology shows caseous necrosis against inflammatory background.

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Figure 3.

MRI images. (a) Axial and (b) sagittal T2 and post contrast images of right pubic bone reveals irregular destruction of both pubic bones (more on right side) is seen involving pubic symphysis with abnormal T2 hyper intense and T1 hypo intense signal. It is associated with T2 hyper intense and T1 hypo intense soft-tissue collection extending inferiorly in the right labia majora with thin peripheral enhancement.

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Figure 4.

MRI images (a) post ATT and (b) after three months show regression of soft-tissue collection and partial resolution of bony change.

Discussion

Next to the lymph nodes, osteoarticular TB is the second most common site of extra-pulmonary TB, ⁴ the spine being the commonest location. Pubic symphysis involvement is rare, ⁵ but not unknown. It accounts for <1% of all musculoskeletal TB^6,7 even in countries where its incidence is high. Thilesen was the first to describe symphysis pubis TB in 1855, followed by Hennies who presented three cases in 1888. Sorelliin, published a series of 32 cases in 1932. ⁸ Immunosuppression leads to an increase in the incidence of extra-pulmonary TB at atypical sites. ³

Pubic bone TB may present as spread from nearby anatomical locations.^7–9 The lesion may present as a non-healing sinus ¹ or as a cold abscess. Extension to the labia is exceptionally rare. Occasionally, an abscess may rupture into the urinary bladder and result in osteuria ¹⁰ and pyuria. ¹¹ Vulvovaginal TB ¹² may present as a labial swelling, though this usually has associated genital involvement, with a large mass, or discharging sinuses, involving bone only in the later stages.

A labial swelling may be a sebaceous cyst, lipoma, folliculitis, simple abscess, soft-tissue tumour ¹³ or rarely an embryonic remnant of the canal of Nuck. ¹⁴ Cytological examination is often diagnostic.

MRI will accurately describe the extent of the lesion, conventional radiology being inconclusive.

Surgical intervention is rarely indicated, but follow-up is advised to confirm healing after adequate ATT.