PO:10:154 | Pudendal nevralgia as an unusual presenting symptom of axial spondyloarthritis

Benedetta Bongiovanni¹, Gabriele Amati¹, Gilda Sandri^1|2, Giovanni Ciancio², Dilia Giuggioli^1|2 | ¹Struttura complessa di Reumatologia, azienda ospedaliera universitaria Policlinico di Modena; ²Cattedra di Reumatologia, università degli studi di Modena e Reggio Emilia, Modena, Italy

Background. The aim of the present study was to describe a case of axial spondyloarthritis (axSpA) presenting unusually with symptoms of pudendal neuralgia.

Case report: S.F., woman, 32 years old. In October 2024, four months after surgical removal of epidermoid cysts complicated by phlegmon in the genito-inguinal region, the patient developed burning and paresthetic pain localized in the inguinal and ischial areas, which later radiated to the genital region, lower buttocks, thighs, and transiently to the legs. Pelvic pain progressively worsened, extending to the perineal and anal regions and severely impaired the ability to maintain a seated position. An electromyography of the lower limbs prescribed by the general practitioner resulted negative. In December 2024, the patient underwent a rheumatologic consultation at our center and a neurology consultation was requested, in addition to routine blood tests. The neurologist, recommended a pelvic magnetic resonance (MRI), suspecting pudendal neuralgia due to possible post-surgical neurogenic injury. MRI findings included: bilateral active sacroiliitis (Figure 1); enthesitis at the insertion sites of tendinous and ligamentous structures at the level of the ischial tuberosity and antero-inferior portion of the pubic symphysis; edema in the adipose tissue underlying the ischiopubic rami and urogenital triangle. No signs of pudendal nerve lesions or space-occupying masses were detected. Laboratory tests revealed: ESR: 60 mm/h; CRP: 1.1 mg/dL; negative rheumatoid factor and anti-citrullinated peptide antibodies. The Schober test was measured at 4 cm. The BASDAI score was 7.6. HLA typing revealed the presence of B35-44 loci. An axSpA diagnosis was made, in accordance with the 2009 ASAS classification criteria, and treatment with adalimumab was initiated. Discussion: Although it is possible that pudendal neuralgia may be part of the symptomatology of axSpA in more advanced stages — due to calcification of the sacrotuberous and sacrospinous ligaments and subsequent entrapment of the nerve within Alcock’s canal — it is highly unusual for it to represent the initial manifestation of axSpA. In the case report, pudendal nerve irritation appears related to extrinsic compression exerted by edema of the tissues underlying the ischiopubic rami and the urogenital triangle, as well as inflammation of the entheses located near the nerve’s anatomical pathway (specifically at the ischial tuberosity and pubic symphysis insertions).

Conclusions: To the best of our knowledge, this is the first reported case in literature of pudendal neuralgia as the presenting symptom of axial SpA. In the differential diagnosis of pudendal neuralgia —which includes repetitive microtrauma, pelvic fractures, pelvic surgery, childbirth, neurological diseases, and neoplastic masses — early axial SpA should also be considered. MRI remains the imaging modality of choice in the differential diagnostic workup.