Salmonella pyomyositis with concurrent sacroiliac osteomyelitis presenting as piriformis syndrome: A rare case.

A-21-year old male admitted with fever and piriformis syndrome, typically associated with gluteal region pain radiating down the thigh, was evaluated and found to have pyomyositis involving piriformis and osteomyelitis with sacroiliac joint affection on radiological imaging. Salmonella serotype typhi was isolated from blood culture. He was treated with intravenous Ceftriaxone for 6 weeks with signs of recovery documented clinically as well as on imaging studies. Salmonella pyomyositis with osteomyelitis in an immunocompetent patient with no previous hematological or endocrine disorder makes this case an unusual presentation.

Introduction

Tropical pyomyositis, a common entity in tropics, is inflammation of affected muscle commonly attributed to Staphylococcus aureus in 95% of cases. Focal salmonellosis affecting muscles is a rare cause of tropical pyomyositis and is more common in diabetics or individuals with underlying malignancy. Early diagnosis and prompt drainage with antimicrobial cover are associated with good outcome, whereas untreated cases are associated with 30% mortality. We report a case of Salmonella pyomyositis involving piriformis with concurrent osteomyelitis, rarely seen together in an immunocompetent healthy male patient who recovered completely following antimicrobial therapy alone.

Case Report

A 21-year-old Asian male with no significant medical history presented to us with complaints of pain in the right gluteal region radiating down to right thigh since 6 days and fever since 2 days. There was no history of recent trauma to lower extremity or back. He denied any history of rash, joint pains, weight loss, or high-risk behavior. History of travel was absent. Family history was noncontributory. There was no history of tuberculosis contact or intravenous drug abuse. There was no history of raw milk consumption or undercooked meat exposure. There was no history of contact with pet animals. On presentation, he was tachycardic and febrile with respiratory rate 24/min and blood pressure 120/80 mmHg. Regional lymphadenopathy was absent. Local tenderness over the right gluteal region was present with no overlying skin changes of inflammation seen. Straight leg raising test was negative. Lower limb reflexes were normal.

Laboratory investigations showed leukocytosis with neutrophilic predominance and eosinopenia (Hb 12.7 g%, total leukocyte count 14,580/cmm, neutrophils 81.7%, and eosinophils 0.1%). Blood chemistry showed normal renal function and electrolyte levels. Malaria antigen test was negative. He was empirically started on intravenous ceftriaxone 2 g 24 h after sending blood culture. Liver function test showed borderline elevated enzymes (serum glutamic oxaloacetic transaminase 62 IU/L, serum glutamic pyruvic transaminase 69 IU/L, and alkaline phosphatase 415 IU/L) with normal bilirubin levels. HbA1C level was 5.5%. C-reactive protein (CRP) was positive (32.37 mg/L) and erythrocyte sedimentation rate (ESR) was raised 34 mm/h.

Chest, pelvis radiographs, and abdominal ultrasonography were unremarkable. Pelvis magnetic resonance imaging (MRI) showed peripherally enhancing fluid collection within the right piriformis muscle measuring 3.2 cm × 3.0 cm size, representing an abscess with subtle bony involvement of the right sacroiliac joint [Figure 1a and b]. Surgical incision and drainage of abscess were deferred taking the small size and deep seatedness of abscess into consideration. Brucella antibodies tested was negative. HIV and hepatitis B surface antigen serology were negative. However, blood culture sent earlier yielded Gram-negative bacilli, later identified to be Salmonella serotype typhi. Ceftriaxone was continued as per antibiotic sensitivity pattern for 2 weeks more following which fever intensity reduced to a significant extent. Meanwhile, Widal test done 1 week after symptom onset yielded significant titers of Salmonella agglutinogens (1:240 Salmonella typhi O, >1:1920 S. typhi H).

Figure 1

(a) Coronal short tau inversion recovery showing right piriformis involvement along with subtle right sacroiliac joint involvement appearing hyperintense as compared to left side. Hyperintense signal is also seen in the right sacroiliac joint space. (b) Axial T1-weight postcontrast image with fat suppression showing right-sided piriformis abscess. (c) Coronal short tau inversion recovery image showing increased hyperintensity of the right sacroiliac joint. Persistent right-sided piriformis involvement is seen. (d) Axial T1-weight postcontrast image with fat suppression showing persistent piriformis abscess with marrow enhancement of visualized right iliac bone

Repeat pelvis MRI after 2 weeks showed no interval change in size of abscess but marrow edema involving iliac and sacral portions of the right sacroiliac joint was more pronounced, with postcontrast enhancement [Figure 1c and d]. Intravenous ceftriaxone dose was stepped up to 2 g 12 h and was continued for 4 weeks more on outpatient basis taking into consideration the deep seatedness of abscess and the bony involvement. After 4 weeks, ESR normalized to 07 mm/h and CRP was negative (0.00 mg/L). Pelvis MRI after 4 weeks showed the signs of resolution with a significant reduction in abscess size and reduced marrow edema of the involved sacroiliac joint [Figure 2a–c]. A gradual improvement was seen clinically, laboratory-wise, and radiologically over 6 weeks course of intravenous ceftriaxone and complete recovery was noted without any complication.

Figure 2

(a) Coronal short tau inversion recovery image showing a significant regression of altered signal intensity in right-sided piriformis muscle. Mild to moderate regression is seen in right sacral and iliac marrow involvement as compared to previous magnetic resonance imaging scan. (b) Axial T1-weight postcontrast image with fat suppression showing mild to moderate regression in marrow enhancement of right sacroiliac bone along with persistent fluid signal in the right sacroiliac joint space. (c) Axial T1-weight postcontrast image with fat suppression showing near complete regression in the right piriformis muscle involvement

Discussion

Salmonella is a nonspore-forming Gram-negative enteric bacillus that is pathogenic for human beings and animals. S. typhi and Salmonella paratyphi cause typhoid and paratyphoid fever and are primarily transmitted through the feco-oral route. Salmonella infection can have systemic spread through two common routes, i.e., spread through the invasion of blood stream or it can enter lymphatics of gastrointestinal tract and spread through lymphatics. Distant abscess formation is a result of hematogenous or lymphatic dissemination of primary gastrointestinal infection.[1] Enteric fever remains the most common clinical manifestation of Salmonella infection. However, focal salmonellosis causing osteomyelitis, pyomyositis, myocarditis, and neuropsychiatric involvement is less commonly seen.[2]

Tropical pyomyositis is characterized by skeletal muscle suppuration with abscess formation, most common etiological agent in 90% cases implicated to be S. aureus. Group A streptococcus is seen in 1–5% cases, other uncommon implications being Streptococcus (Groups B and C), pneumococcus, Neisseria, Haemophilus, Aeromonas, Pseudomonas, and Klebsiella.[34] Rarely Salmonella, Fusobacterium, and anaerobes are seen.[5] Diabetes mellitus, immunosuppression, cancer chemotherapy, underlying HIV infection, trauma, steroid use, and dialysis are known risk factors for pyomyositis.[6] Muscles commonly involved are glutei, abdominal and spinal muscles, quadriceps, pectoralis, iliopsoas, and gastrocnemius. Clinically, pyomyositis is divided into three stages: (a) invasive stage characterized by subacute onset, firm swelling with no erythema, minimal pain, and dry tap on aspiration at times; (b) suppurative stage characterized by abscess formation, high-grade fever spikes, and increased severity of symptoms; and (c) late stage, in untreated cases, may lead to disseminated bacterial infection followed by septicemia and septic shock with metastatic abscesses.[7] S. typhi is a common cause of osteomyelitis in patients with sickle cell anemia. Rarely, bacterial isolation of Salmonella is seen in nonsickle cell patients. A review of literature shows very few cases of sacroiliac osteomyelitis with or without concurrent pyomyositis due to Salmonella infection in a patient with no underlying hematological, immunosuppressive, or endocrine disorder.[89]

Early diagnosis and appropriate treatment with the adequate antibiotic course and prompt surgical drainage as required are essential to reduce the mortality associated with pyomyositis. Substantially high mortality (~ 30%) associated with Salmonella pyomyositis was reported as compared to other bacterial pyomyositis by Collazos et al.[10]

Piriformis syndrome is a neuromuscular condition characterized by low back, hip, buttock, and leg pain and is often misinterpreted as sciatica. Although the most common cause of sciatic pain is discogenic, the nondiscogenic cause, i.e., piriformis syndrome, is often overlooked as a diagnosis.[11]

Conclusion

We report a case of Salmonella pyomyositis with concurrent sacroiliac osteomyelitis presenting as piriformis syndrome in an immunocompetent nondiabetic patient, which to our knowledge has been rarely reported.

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Conflicts of interest

There are no conflicts of interest.