Coccygeal Vertebral Tuberculosis

Sir, Vertebrae are the commonest site of skeletal tuberculosis[1] and the vast majority of them occur in the thoracic and lumbar spine. Isolated coccygeal tuberculosis is a very rarely reported entity.[1–4] A 73-year-old lady with history of chronic kidney disease on maintenance hemodialysis had history of intermittent episodes of low-grade fever for the last 8 months. There was no definite history of decreased appetite or weight loss. Several investigations evaluating the cause of fever were noncontributory. She had been put on a prolonged course of doxycycline and after a brief period of response, her fever had relapsed. She developed progressively increasing coccygeal pain for 1 month duration, which increased on sitting. A magnetic resonance imaging (MRI) scan showed destructive lesion of the coccyx with a precoccygeal collection that was hyperintense on T2-weighted sequences and hypointense on T1-weighted sequences [Figure 1]. The rest of the spine showed no lesion. Fluorodeoxyglucose positron emission tomography (PET) scan showed tracer uptake in the coccyx only. Computed tomography (CT) scan showed a destructive lytic lesion in the coccyx with precoccygeal collection [Figure 1]. The patient underwent CT-guided aspiration of the collection, which showed presence of acid-fast bacilli (AFB) on Ziehl–Neelsen stain. GeneXpert (nested polymerase chain reaction) for tuberculosis was positive. The patient was started on four-drug regimen (rifampicin, isoniazid, ethambutol, pyrazinamide), which was continued for 2 months, and is currently on three-drug regimen (rifampicin, isoniazid, ethambutol). Her pain and fever both subsided within 2 weeks of initiating treatment.Figure 1: Sagittal T1-weighted (a) and T2-weighted (b) sequences showing precoccygeal collection (green star) with coccygeal involvement and destruction (orange arrow). The collection is hypointense on T1 and hyperintense on T2 sequences. Axial T1 (c) and axial T2 sequences (d) also show precoccygeal collection (green star). (e) short tau inversion recovery (STIR) sequences show only coccygeal involvement and no sacral involvement, and CT scan of sacrococcygeal vertebrae (f) shows lytic lesion in the coccyx (orange arrow) with precoccygeal collection (green star)A PubMed search using the terms “coccyx and tuberculosis” yielded only eight results. In three cases, there was additional sacral involvement as well, while in one case, there was also involvement of the lumbosacral vertebrae. In the rest, as in our patient, the coccyx was the only site of vertebral tuberculosis.[1–4] These cases are summarized in Table 1.Table 1: Summary of cases of coccygeal TB described in literatureTwo of these cases presented with discharging sinus in the perineal region,[1,4] while three of them had coccygeal pain.[1–3] Our patient too had coccygeal pain, but her primary complaint was pyrexia of unknown origin, for which previous investigations were noncontributory, which was not described previously. Other systemic symptoms like weight loss or anorexia, which are known to occur in tuberculosis, have not been reported in any of the cases previously described in literature. Takakura et al.[5] have stressed the importance of considering sacrococcygeal tuberculosis as an etiology in nonhealing and recurrent perineal fistulas, while Osman et al.[6] and Gadi et al.[7] have reported that as neurologic deficits are uncommon in isolated sacrococcygeal tuberculosis and as nonspecific pain is the commonest symptom, there is a delay in diagnosis of this lesion. MRI of the whole spine in addition to lumbosacral spine is the mandatory to stamp a diagnosis of isolated coccygeal involvement as there may often be skipped involvement of vertebrae at several levels.[7] Radiologic differential diagnosis of these lesions would include spreading pyogenic infections from the anorectal area, neoplasms,[5] and metastases (particularly in older patients like our case). Final confirmation of the diagnosis by cytology, histopathology, or culture is mandatory as starting empirical antituberculous treatment is usually not recommended.[8] In one patient, the diagnosis of coccygeal tuberculosis was made after surgery (exploration of sinus tract and debridement),[4] while in other cases as in ours too, CT-guided biopsy was sufficient to establish the diagnosis.[1–3] Our case demonstrated AFB on staining of the pus, and nested polymerase chain reaction was also positive for mycobacterial DNA. This is a validated tool for diagnosis of tuberculosis and is of use when scanty bacterial load is present.[9] The utility of similar PCR-based tests has been reported by Takakura et al.[5] also, who emphasized that it may lead to avoidance of open surgery. Tubercle bacilli reach the vertebrae through the bloodstream (either through arteries supplying the marrow or retrograde via the Batson’s plexus), and hence, paradiscal variant (at the site of the hairpin loops of supplying vessels) is the commonest type of vertebral involvement.[10] The rarity of coccygeal tuberculosis can be explained both by its small size relative to the entirety of the vertebral column (the thoracic spine with 12 vertebrae and the lumbar spine with five of the largest vertebrae are naturally more commonly affected) and because it consists of predominantly cortical bone with very little blood flow compared to other regions of the spine that have greater cancellous marrow. All the patients described in literature had symptoms for a long time before a diagnosis was reached. This is partly because the mainstay of treatment in coccydynia is conservative management[11] and also as patients often live with fistulas for a long time before seeking definitive treatment. The duration of antitubercular treatment (ATT) is not standardized for coccygeal tuberculosis. While common sense would dictate that the regimen be in line (both in nature and duration) to that used in extrapulmonary skeletal tuberculosis, various authors have given ATT for 6,[2] 9,[3,5,6] and 15 months.[1] We intend to continue treatment for 18 months to prevent any recurrence as is our protocol for vertebral tuberculosis at any other location. Though isolated tubercular involvement of the coccyx is a rare entity, in countries where tuberculosis is endemic, all cases of recalcitrant coccydynia and nonhealing perineal sinuses must undergo imaging to see for any destructive lesion in the coccyx [Table 1]. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.