Tuberculosis of ischial tuberosity as a rare cause of gluteal pain: A case series of 9 patients with review of literature

Abstract

Background

Osteo-articular Mycobacterium tuberculosis infection of the ischial tuberosity is a rare cause of gluteal pain.

Methods

A retrospective clinico-radiological review of nine patients with Mycobacterium tuberculosis infection of the ischial tuberosity was undertaken. The spectrum of presenting features, diagnostic challenges, radiological findings with particular emphasis on Magnetic resonance imaging (MRI) and clinical course was reviewed.

Results

All the 9 patients (5 male: 4 female) aged between 8 and 50 years of age (mean 15.3 years) developed insidious onset of buttock pain over a period of weeks to months with difficulty in walking. Microbiological and/or histopathological confirmation of Mycobacterium tuberculosis infection was undertaken in all cases. Complementary MRI revealed diffuse bone marrow signal hypointense or isointense on T1-weighted and hyperintense on T2-weighted and STIR images. MRI was able to provide anatomic details of soft tissue lesions and extensions. MRI illustrated the sinus tract in one patient. Ultrasound imaging allowed diagnostic and therapeutic management of in 3 patients.

Conclusion

Tuberculosis of ischial tuberosity can be a rare cause of gluteal pain. Delay in diagnosis could be due to an indolent natural history, unusual presentation and clinical features. A high index of suspicion especially in endemic areas with complementary imaging and microbiological or histopathological confirmation of Mycobacterium tuberculosis infection is necessary for definitive diagnosis. Targeted treatment under the umbrella of Anti-Tubercular Therapy is crucial in achieving successful clinical outcome.

1. Introduction

The musculoskeletal system (MSK) is the most common extrapulmonary site involved in Mycobacterium tuberculosis (TB). MSK-TB accounts for 20–40% of all extrapulmonary TB cases and 1–3% of all TB cases.^1,2 The spine is the most affected site (more than 50%) followed by the weight bearing joints of the pelvis, hip, knee, and ankle/foot (10%–13% each).³ Amongst the uncommon sites, TB osteomyelitis of the ischial tuberosity (IT-TB) is rare, constituting only about 0.1–0.43% of all MSK -TB.^4,5 A total 21 cases have been reported in the English literature databases (Table 1).^{4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19}

Table 1.

Previously reported cases of tuberculosis of ischial tuberosity in English literature.

Author/Year	No of cases	Age/Sex	Side	Symptoms	Radiology	Diagnosis	Treatment	Outcome	Remark
Kaplan 19366	1	33/M	Rt	H/o fall. Swelling buttock Sinus buttock Fistula	XR: Destructive area with circumscribed wall with soft tissue mass with fracture	Guinea pig inoculation Tubercle Bacilli	Incision and drainage, Roentgen therapy	Cured	Ghon tubercle in chest
Magnusson 19387	3	34/M	Lt	Mild pain, Fistula	NA	NA	Conservative	Healed	Pulmonary tuberculosis (TB)
		6/M	Rt	Mild pain, Fistula	XR: Sequestrum		Sequestrectomy	Healed	TB left knee
		24/M	Rt	Mild pain, Fistula	XR: Sequestrum	Tuberculosis on histology	Sequestrectomy	Healed
Tupman 19538	1	20/F	Rt	H/o trauma + Aching pain x 13 months followed by Recurrent enlarging swelling buttock Sinus	XR: Rarefaction ischial tuberosity, sequestration	Pus: AFB	Curettage, sequestrectomy with local and systemic streptomycin	One year asymptomatic	H/o epilepsy
Lafand EM 19585	1	NA	NA	NA	NA	NA	NA	NA
Tuli and Sinha 19694	1	Young/F	Rt	Pain Swelling Discharging sinus buttock	XR: cavitary lesion with soft coke like sequestrum	NA	ATD	NA
Bhattacharya 19739	3	15/F	Lt	Swelling medial aspect thigh 1.5 years Pain buttock x 1.5 months Sinus –discharging pus	XR: Irregular area of destruction involving the ischial tuberosity	HPE: TB Pus culture: Tubercle Bacilli	Curettage ischium, sinus tract excision. Triple ATD- streptomycin, INH, PAS	Healed	Recurrence after 1.5 years
		25/F	Rt	Pain buttock while sitting x 6 months Weight loss x 3 months	XR: Cavity in the ischium, with an irregular margin and patchy surrounding sclerosis	HPE: TB	Ischium curettage with ATD
		20/F	Rt	Radiating pain down the lower Limb Swelling medial aspect thigh X 9 months	XR: Destruction with cavity formation	HPE:TB, abscess aspiration: tubercle bacilli	Drainage cold abscess, ATD Ischium curettage	–
Silva JF 198010	1	NA	NA	NA	NA	NA	NA	NA	NA
Samar G 198511	1	6/M	Lt	H/o Trauma + Pain buttock x 3 months	XR: Irregular lytic area with minimal expansion ischium with speckled areas of increased density tiny sequestrae	HPE:TB and multiple sequestraes	ATD- tripple drug regimen- Isoniazid, Ethambutol, Streptomycin. Curettage and biopsy	Healed	Right paratracheal Lymphadenopathy
Garcia 199412	1	71/M		Persistent pain groin x 6 months Weight loss +	XR: Osteolytic lesion of ischium Tc99 bone Scan: increased uptake	HPE: TB LJ media negative	Curettage + ATD (2 drugs Ethambutol + Pyazinamide) 2 months + HREZ for 6 mo	3 years follow up good outcome	Differential diagnosis (dd)- Bone tumor, osteitis, metastasis
Vohra R 199713	2	18/F	Rt	NA	XR: Osteolytic lesion with sequestrum	HPE: TB	ATD	–	DD- Brodie abscess
		35/F	Rt	NA	XR: bone loss but no bone production in the ischium	HPE:TB	ATD	–	Metastasis, Ewing's tumor or plasmacytoma
Toda K 199814	1	77/M	Lt	Lump buttock, increasing to 10 cm size over 1 month	XR: Bone defect ischium CT scan: homogeneous low density, several nodules in muscle Post-Contrast CT: Marginal enhancement MRI: T1-w- low signal T2-w- high signal MR images with Gd- DTPA enhancement: wall enhancement	HPE:TB Ziehl-Neelsen stain tuberculous bacilli	Complete resection of lump with partial resection of ischium ATD	–	Past h/o Pulmonary TB Presented as tumor
Franco M et al. 200115	1	67/F	Lt	Intermittent fever, night sweats x 10 months Pain buttock on walking and sitting.	XR: Ischiatic cortical Irregularities; Tc 99 m Scan: Mildly increased uptake ischium CT scan: lytic lesion ischium, Soft tissue mass, calcification MRI: low-signal intensity, heterogeneous on contrast	CT biopsy caseating granulomas Culture: TB	ATD 12 months (HREZ 2 months. HR for 10 months)	14 months recalcification	On Dialysis
Krishnan 201016	1	35/F	Rt	chronic gluteal pain associated swelling	XR: osteolytic lesion Rt ischial tuberosity and soft tissue swelling around the proximal right femur and hip with areas of calcification CT and MRI multiseptate, multilobular, rim-enhanced mass lesion Rt buttock, with soft tissue changes and erosion	HPE epithelioid cells and Langhan's giant cells consistent with tuberculosis culture: negative	Debridement, curettage followed by ATD for 12 months	consolidation of the lesion at 4 years follow
Mandeep SD201617	1	18/M	B/L	gluteal pain, fever, weight loss	XR: lytic lesion on Lt and on the Rt indistinct margins; MRI: involvement of both IT with changes in signal intensity; collections in various intrapelvic and extrapelvic planes bilaterally	HPE: polymerase chain reaction (PCR) of the aspirate obtained by computed tomography (CT)-guided FNA epithelioid granulomas and the genome of mycobacteria grown	Conservatively 18 months of ATD	Complete healing at 18 months	Review of MRI scans showed signs of healing TB.
Mulder et al. 201718	1	66/F	Lt	Progressive left sciatic pain, radiating to the back of leg X 6months	XR: Normal CT: fluid collection, located superficial to the left gluteus maximus muscle, with a fistula to the LtIT ischial tuberosity. MRI: abcedation with connection to the IT and chronic osteomyelitis	Ziehl-Neelsen (ZN) staining negative; BacT/Alert MB® positive for M.TB HPE: non-specific subcutaneous necrotic tissue	Triple therapy with ethambutol, isoniazid, and rifampicin for 18 months	Not given	drug resistance to pyrazinamide
Murugan C et al. 202119	1	27/F	Rt	4 months history of progressive right buttock pain	XR: eccentric, lytic lesion with ill-defined margins in the Rt IT MRI: altered marrow signals in the Rt IT with significant enhancement and edema in the surrounding soft tissue with two pockets of pus collection	HPE: Langerhans giant cells and epitheliod cells consistent with TB. AFB culture: negative for tubercle bacilli.	Debridement; ATD 9 months	Follow-up at 3 years: No recurrence

Abbreviations: M = Male; F = female; Rt = Right; Lt = left; B/L = Bilateral; yr = year; Mo = months; AFB = Acid Fast Bacilli; ATT = Anti tubercular therapy; DOTS: Directly observed treatment, short-course; PCR= Polymerase Chain Reaction; MTB = Mycobacterium tuberculosis; USS= Ultrasound; LN = Lymph node; CECT: Contrast-Enhanced Computed Tomography; MRI = Magnetic Resonance Imaging; FNAC= Fine Needle Aspiration Cytology; H- Isoniazid; R- Rifamipcin; E− Ethambutol; Z- Pyrazinamide; S- Streptomycin; NA= Not available; IT = ischial tuberosity; ZN staining = Ziehl-Neelsen staining; HPE = histopathological examination.

Ischial tuberosity is a rounded bony protuberance arising from the from the postero-inferior part of the ischium giving attachment to proximal origin of the hamstring tendons. It is one of the contents of the Gluteal region along with other structures (Fig. 1, Fig. 2). Gluteal (buttock) pain can be caused by a myriad of pathologies. The source of gluteal pain can be due to referred pain from pathologies originating from the spine or the anatomical structures that constitute the gluteal region such as skin, fat, ischial bursa, muscles, hamstrings tendons or osseous elements itself.²⁰ The borders of the gluteal region are defined by the following landmarks: (i) posteriorly, the gluteus maximus muscle (ii) anteriorly, the posterior hip joint and capsule, (iii) laterally, lateral the lip of Linea aspera and gluteal tuberosity, (iv) medially, the sacro-tuberous ligament (ST), (v) superiorly, the inferior margin of the sciatic notch, (vi) proximally, the origin of the hamstring muscles at the ischial tuberosity (Fig. 1, Fig. 2). Local pathologies such as boils/furuncles/abscesses, proximal hamstring injuries with or without avulsion of ischial tuberosity, Ischiogluteal bursitis, entrapment of the sciatic nerve, piriformis syndrome and very rarely tumours are customary causes of gluteal pain.²¹ Pyogenic osteomyelitis of the ischial tuberosity is common and usually due to contiguous infection from decubitus ulcers.²²

Fig. 1.

Diagrammatic representation (Sagittal section) through the structures of the Gluteal region. SAR-Sartorius, AL-adductor longus, AM-adductor magnus, A MIN-adductor minimus, IL-ilium, FEM A/V- femoral neurovascular bundle.

Fig. 2.

Diagrammatic representation (Coronal section) through the structures of the Gluteal region. Gr- Gracilis, AM-adductor magnus, GLU MAX – Gluteus maximus, PIR-piriformis, SN- sciatic nerve, IT-ischial tuberosity, OI- obturator internus, SM-semimembranosus, CT-conjoint tendon.

Characteristically, the primary source of TB osteomyelitis are the lungs, however IT- TB may result from the spread of adjacent infective foci in the gluteal region.

IT-TB's rare incidence, unusual location, insidious onset, subtle nature of symptoms along with unfamiliarity on part of the clinician, make the diagnosis of IT-TB difficult. Pain and local swelling are the most common presenting complaints whereas constitutional symptoms of TB including weight loss, low grade fever, malaise and night sweats are less frequent.

We would like to highlight the clinico-radiological features, management strategies and follow-up adopted in this series of nine patients with IT-TB. The description would emphasize the necessity to suspect tubercular osteomyelitis as one of the uncommon causes of gluteal pain. IT-TB can be easily missed but complementary imaging can assist in effective diagnosis and management of the condition.

1.1. Search strategy and criteria

We performed a systematic review of English language articles of TB of the ischial tuberosity

From 1936 to 2021 using the terms, ‘Mycobacterium tuberculosis’, ‘‘tuberculosis” and “ischial tuberosity”, and “Gluteal abscess,” on the search engine of PubMed and Scopus databases (Table 1). We identified 21 cases published in the English literature most have been single case reports.

2. Identification of patients

Institution 2 search was done through the Computerized Radiology Information System (CRIS) system. In the remaining cases, patients were identified from the Hospital medical database.

3. Case description of patients in the study

The age of the nine patients assessed in the study ranged from 8 to 50 years (mean 15.3 years). (Table 2). Five were male and four were female. Five patients were of paediatric age group (8–12 years). The clinical presentation was an insidious onset over a variable period from 4 weeks to 1 year in most patients. Commonest presenting symptoms were of gluteal pain and difficulty in sitting. There was a history of an obvious swelling (Case number 1,7), limp and wasting (Case 6,8) and sinus formation (Case number 3). The 3 cases (7,8,9) had extensive unclassified type of hip tuberculosis with ischial tuberosity involvement. These patients presented with stiffness and muscular spasm. Constitutional symptoms were present in two patients (Case 1 and Case 2) and all the patients were immunocompetent. All the patients underwent plain radiologic examination; however only in three cases did these reveal obvious, lytic lesions of the ischial tuberosity. (Fig. 3 a). In one (Case 6) the lytic lesion was associated with pathological fracture. MRI of the pelvis was undertaken in all patients except in cases 6,7,9. MRI demonstrated features of altered bone marrow signal in the ischial tuberosity which appeared hyperintense on fluid sensitive sequences and low on T1 imaging. There was mild soft tissue edema of the surrounding muscles. (Fig. 3 b,c, Fig. 4, Fig. 5, Fig. 6). In case 9 computed tomography (CT) helped in confirming radiograph lesion. In three cases (7,8,9) the disease was extensive at the presentation and involved hip and surrounding structures. The diagnosis was confirmed by culture of the aspirate on Lowenstein–Jensen growth medium for Mycobacterium tuberculosis (Case 1,2 and 5). Histological evidence with Fine Needle Aspiration Cytology (FNAC) was undertaken in six patients (Case 2- complementary corroboration from lymph node biopsy and Case 4 underwent diagnostic FNAC) in rest four cases biopsy was confirmative for diagnosis of tuberculosis. Polymerase Chain Reaction (PCR) test was used as a diagnostic modality in Case 3 and to verify diagnosis in Case1 and 2. The Case 1 underwent ultrasound (US) guided aspiration of the symptomatic collection on the medial aspect of the right thigh. All patients were initiated on a supervised antituberculosis chemotherapy (ATT) with a four-drug regimen of (rifampicin, isoniazid, pyrazinamide, and ethambutol) for 2 months followed by three drugs (isoniazid, rifampicin, and ethambutol) for a further 10 months. All patients remain asymptomatic at 2-year follow-up evaluation.

Table 2.

Summary of patients Mycobacterium tuberculosis infection of the ischial tuberosity.

Cases	Age/Sex	Side	Clinical features	Radiology	Laboratory reports	Diagnosis	Treatment	Follow-up and outcome	Remarks
Case1	50/M	Rt	Mild pain Gluteal since 1 yr; swelling inner part of upper thigh region since 2 Mo; difficulty in walking and pain while sitting; low grade fever on and off with weight loss and anorexia	Radiograph: lytic lesion in right ischial tuberosity: MRI: altered signal intensity in ischial tuberosity appears hyperintense on T2 and isointense on T1. A multiseptate collection is also noted medial proximal part of thighs communicating with the right ischial tuberosity lesion	Anaemia with lymphocytosis Raised ESR and CRP	Positive MTBculture and PCR for MTB	USG guided aspiration of abscess; ATT from DOTS for 12 months	2.5 year; Lesion healed with surround sclerosis	Family history of TB in spouse; Past history of pleural effusion 22 year back which was treated for 6 Mo with ATT
Case 2	14/F	Lt	Pain Gluteal last 4 weeks; difficulty of sitting in a classroom; history of enlarged cervical swelling Lt, abdominal discomfort, and weight loss over last 5 months	CECT scan abdomen and thorax: multiple conglomerated necrotic enlarged LN; Pelvis radiograph: lytic lesion in the ischial tuberosity; MRI pelvis: marrow edema left wall of the acetabulum, ischial tuberosity, and inferior pubic rami.T2 signal changes in the surrounding muscles and a small thick collection in the left ischial tuberosity	ESR: 12 and Mantoux test Positive	FNAC cervical region suggestive of multiple epithelioid granulomas with multinucleated giant cells, culture from lymph node aspirate MTB, PCR positive for MTB	ATT from DOTS for 12 months	2 year; Lesion healed	Concomitant TB of LN of cervical, thoracic and abdominal region
Case 3	19/M	B/L	Sinus in perineal area with bilateral Gluteal pain	MRI: Diffuse marrow signal in B/L ischial tuberosity, pubic symphysis	ESR: 30 Mantoux positive CRP positive	PCR positive AFB negative Culture- negative	ATT from DOTS for 12 months	2 Year Lesion healed; Sinus healed	Nothing specific
Case 4	10/F	Rt	Ischial/Gluteal pain Initially, referred to tumor centre for opinion	MRI: Marrow edema in the ischial tuberosity, no soft tissue collection	FNAC Biopsy Raised ESR	Histological Confirmation of MTB	ATT for 12 months	Asymptomatic at follow-up	NA
Case 5	12/M	Rt	Gluteal Pain	MRI: Multiple foci of osseous edema in the pelvis including ischium and surrounding soft-tissue collection	Aspiration of collection Raised ESR	AFB and Culture Positive	ATT for 12 months	Asymptomatic at Follow-up	NA
Case 6	8/M	Rt	Limping 4 months; flexion hip >90° painful; wasting right gluteal muscles; duration 4 months	X ray: Lytic lesion ishium and pathological fracture	Hb 8.8 gm% ESR 60 mm	Biopsy confirmation	ATT for 12 months	Asymptomatic at Follow-up	Pathological fracture healed
Case 7	8/F	Lt	Restriction of hip movements; fluctuation in buttock region	X ray: Extensive lesion involving the hip joint and ischial bone	Aspiration of collection	Biopsy confirmation	ATT for 12 months	Asymptomatic at Follow-up
Case 8	8/M	Rt	Limp; stiff hip	X ray: Extensive lesion involving the hip joint and ischial bone; MRI confirmed above findings	Raised ESR	Biopsy confirmation	ATT for 12 months	Asymptomatic at Follow-up
Case 9	9/F	Rt	Gluteal abscess- drained elsewhere; stiff hip	X ray: Extensive lesion involving the hip joint and ischial bone, CT confirmed above findings: irregular lytic lesion involving acetabulum, ischium with cortical irregularities, periosseous collection, mild joint effusion and edematous periarticular muscles	Raised ESR	Biopsy confirmation	ATT for 12 months	Asymptomatic at Follow-up

Abbreviations: M = Male; F = female; Rt = Right; Lt = left; B/L = Bilateral; yr = year; Mo = months; ESR = Erythrocyte Sedimentation Rate; CRP= C-reactive protein; AFB = Acid Fast Bacilli; ATT = Anti tubercular therapy; DOTS: Directly observed treatment, short-course; PCR=Polymerase Chain Reaction; MTB = Mycobacterium tuberculosis; USS= Ultrasound; LN = Lymph node; CECT: Contrast-Enhanced Computed Tomography; MRI = Magnetic Resonance Imaging; FNAC= Fine Needle Aspiration Cytology.

Fig. 3.

AP radiograph of pelvis (a) showing lucency in the left ischium Coronal T2FS (b) and axial T2FS(c) showing fluid collection superficial to the ischial tuberosity.

Fig. 4.

Coronal T2(a), T2FS sagittal (b) and axial (c) showing large collection (arrow) within the proximal hamstrings.

Fig. 5.

Axial T1(a) and STIR (b) showing osseous edema of right ischium with collection (arrow).

Fig. 6.

AP radiograph of pelvis showing lucency in the right ischium (A) Coronal T2 (B) AP radiograph of pelvis showing healed lesion right ischium after 18 months ATD (C) clinical image showing cross leg sitting without discomfort.

4. Discussion

A detailed review of English literature reveals 21 published articles in the form of either one or two case reports of TB affecting the ischial tuberosity. This suggests the uncommon or rare occurrence of IT TB. Tuli and Sinha describe the incidence of IT- TB to be 0.1% of all skeletal TB while Magnusson estimated an incidence of 0.27% and Lafond quoted it to be 0.43%.^4,5,7,9 There does not seem to be any specific age predilection for this condition. (Table 1). Though literature suggests IT -TB to be uncommon in the paediatric age group, 5 of the patients in our series were of paediatric age group.

Majority of patients had symptoms of insidious onset, dull buttock pain with difficulty in sitting on hard surfaces. However as the disease progressed; the pain was present at rest and even while sitting on a soft mattress. This suggests localized inflammation of the ischial tuberosity and its associated bursae. The pain radiated to the back of the thigh in 3 patients suggesting either the irritation of the adjacent sciatic nerve due to an inflammatory process or extension of the disease process along the anatomical planes. This feature of referred pain could be mistaken for pain associated with lumbar radiculopathy or sciatica and can lead to a delayed diagnosis of IT-TB. Constitutional symptoms associated with Mycobacterium TB infection are uncommon in TB affecting peripheral osteoarticular structures owing to the slow nature of the disease process. In the literature review, only 4 patients had constitutional symptoms reported at presentation.^9,12,15,17 In the present series constitutional symptoms were found in Case 1 and Case 2 corresponding with the background history of pulmonary TB in the past and features widespread TB lymphadenopathy, respectively. This suggests a distant reactivation of TB at the Ischial tuberosity in our patient though without a precipitating cause after a disease-free interval of 22 years.

In the other patient, (Case 2) IT-TB was a part of multi-system involvement of Mycobacterium TB infection with a primary focus of infection located in cervical, hilar, peripancreatic and paraaortic lymph nodes. A Fine Needle Aspiration Cytology (FNAC) needle cytology of the cervical lymph node confirmed the diagnosis of Mycobacterium TB.

Distant presentation away from the primary site of Mycobacterium TB is a well-known phenomenon associated with osteoarticular TB in the form of a cold abscess, sinus or non-healing fistulae.²³ Cold abscesses are characterized by lack of pain and other signs of inflammation. They sometimes may be the only presentation or become visible in the form of a sinus, being often misdiagnosed as pyogenic infection.²⁴ The exudative process from the disease spreads along the anatomical, fascial planes leading to the distant presentation away from the original site of infection. This was observed in two of our patients (Case 1 and Case 3). In the first patient, a multiseptated collection was noted medial proximal part of thighs communicating with the right ischial tuberosity lesion. The disease had spread deep to the membranous layer of the superficial fascia along the adductor muscle to present itself in the medial, inner thigh. In the other patient (Case 3), the disease spread to the skin and presented as sinus in the peri-anal area along the fat planes. In literature, the majority of patients with IT-TB swelling appeared months after the pain. A total of 7 patients had complaints of swelling or lump in the buttock or upper thigh while a similar number of patients (7) had skin changes over ischial tuberosity in the form of sinus (Table 1).

Plain radiographs tend to be the first line of radiology imaging in osteoarticular TB. However, there are no specific radiographic features that are pathognomonic of TB of bones or joints.²³ The initial radiographs may be normal or have surrounding osteopenia. As the disease progresses, the radiographic features include irregular areas of destruction with cavity formation with or without sequestrum. Bone destruction and lytic lesion due to the disease process were evident in three of our patients (Case 1, Case 2 and Case 3). This suggests the duration of the underlying disease and the time it has taken to initiate the radiological changes. Complementary imaging with Computed Tomography scan (CT Scan) and MRI provides significant advantages in diagnosis of IT-TB. CT scan can detect abnormalities earlier than plain radiography and allows the evaluation of the osseous or joint involvement.^25,26 However it involves radiation. MRI with or without contrast enhancement is the diagnostic modality of choice. MRI may diagnose the IT-TB even before radiographic changes develop as it may show changes of infection in the bone marrow. These changes are isointense or hypointense on T1-weighted and hyperintense on T2-weighted and STIR images. MRI provides anatomic details of bone lesions, associated abscess or soft tissue mass and path of fistulous tract if present.^14,27 MRI may also highlight other pathologies seen in the gluteal region with their characteristic features.

A diagnosis of Mycobacterium TB requires a microbiological and or is characteristic histopathological (HPE) features on a biopsy specimen. Due to the paucibacillary nature of Mycobacterium TB, it may not be possible to develop a positive culture on the traditional Lowenstein–Jensen growth medium for Mycobacterium tuberculosis. However, in such situations new modalities such as PCR or Enzyme-linked immunosorbent assay (ELISA), a immunological antibody assay can be employed. PCR can detect the mycobacterium earlier than the culture methods and allow early start of treatment. We utilized PCR tests in our patients to provide supportive diagnostic evidence of Mycobacterium tuberculosis. PCR is 100% specific for Mycobacterium TB and helpful in ruling out atypical Mycobacterial infection.²⁸

The pathognomonic features for diagnosis of Mycobacterium TB on HPE include caseating necrosis with surrounding Langerhans and epithelioid cells. With the advent of drug resistance to commonly used antitubercular medications, drug sensitivity tests are recommended especially in patients from endemic regions to achieve appropriate chemotherapy response. We performed this in two patients (Case 1 and Case 2). This was because of the previous history of TB in the first patient and the presence of multisystemic disease in the other. Both responded well to the supervised ATT regime.

Currently, the treatment of the IT-TB is supervised, ATT with supportive care. Symptomatic collections are aspirated or drained under the cover of ATT usually under ultrasound guidance. We undertook this in one patient of ours in the series (Case 1). All patients were initiated with ATT regimen as per the Index TB guidelines.²⁹ This consisted of a four-drug regime of (Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol) for initial 2 months followed by three drugs (Isoniazid, Rifampicin and Ethambutol) for a further 10 months. The patients on ATT regime were monitored for side effects and with laboratory parameters. The type of drugs and duration of ATT in a review literature reveals a wide spectrum of management strategies.

The patient should be followed-up in a regular time period for non-responders, healed status disease and for any recurrence. The present case series showed that the diagnosis of ischial TB should be suspected in patients with gluteal pain. Ischial TB can occur as a part of extensive hip disease. Plain radiograph may be sufficient in situations with features of osteolytic lesions and associated clinical features of TB. However, if the diagnosis is in the doubt; complementary imaging such as MRI or CT scan can be taken to further strengthen clinico-radiological findings. The diagnosis can be confirmed by aspiration of an abscess or biopsy of the lesion with or without ultrasonography. After the confirmation of diagnosis of Mycobacterium TB, the patient can be managed with standard Anti-Tubercular Therapy and regular follow-up.

5. Conclusion

The deep-seated nature of ischial tuberosity along with a slow, indolent course of Mycobacterium TB of Ischial tuberosity is a challenging condition to diagnose and treat. Mycobacterium TB osteomyelitis of the ischial tuberosity is a rare entity and an uncommon cause of gluteal pain. A high index of suspicion, elucidating a detailed history and careful clinical evaluation can allow localization of the condition. Multi-modality, especially MRI imaging, allows to delineate extent of lesion. Microbiological and/or histopathological confirmation of Mycobacterium TB infection of the ischial tuberosity. Targeted, supervised treatment under the umbrella of Anti-Tubercular Therapy and clinical monitoring allows effective management of the condition.

Declaration of competing interest

None.