Sacroilitis in Preschool Children: A Case Series and Review of the Literature
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pyogenic sacroilitis is an infrequent osteoarticular infection, and its diagnosis is a challenge in young children. A series of 20 cases is described. The median age was 15 months, 75% of them being under 2 years old. Fourteen (70%) reported fever. Refusal to sit was the main reason for consultation. Final diagnosis was confirmed by bone scintigraphy. All patients achieved a complete resolution without sequelae.
Pyogenic sacroiliitis (PSI) is a rare condition. It accounts for approximately 1%–2% of septic arthritis (SA) in pediatric age1 and is slightly more common in males.2 The clinical picture varies depending on the age of the patient, establishing 2 main groups: infants and toddlers and older children.2,3 In older children, hematogenous dissemination has been described as the main route of dissemination. However, pathophysiology of PSI is not well known in younger children. Staphylococcus aureus is the most frequently involved microorganism although studies in PSI are scarce and, on the other hand, the involvement of other agents has been described.4
The unspecific symptomatology is a challenge and leads to a considerable diagnostic delay on many occasions. Therefore, a high index of suspicion is necessarily based on the anamnesis, physical examination and laboratory tests. Diagnostic confirmation requires imaging techniques, the yield of blood cultures being very low. The clinical outcome, following an early diagnosis and an adequate therapeutic approach, is successful.
Recently, 2 series have been published mentioning the importance of this entity in children.2,3 Donzelli et al2 established the age of 4 years as a cutoff point with relatively well-defined clinical characteristics, and in which Kingella kingae has been described as the most frequent causative agent of osteoarticular infections (OAIs),5 mild course and better outcome.6 These conditions could allow considering oral treatment. However, data on PSI in young children remain limited and treatment regimens and outcomes have not been well described. The aim of this study was to assess the clinical characteristics and outcome of patients under 4 years old diagnosed with PSI over an 18-year period in a pediatric rheumatology unit in a tertiary hospital, evaluating entirely oral treatment as an effective option in selected cases.
MATERIALS AND METHODS
A retrospective review of the database of our pediatric rheumatology unit between January 2000 and December 2018 was performed. Regarding the diagnosis of sacroiliitis in children ≤16 years, ICD9 code 720.2 was searched. For the diagnosis of osteomyelitis and septic arthritis, ICD-9 codes 730 and 711, respectively, were retrieved. All cases of PSI identified among children under 4 years old were included.
PSI was defined as the presence of suggestive symptoms (limp, refusal to sit, night irritability and unilateral buttock support) accompanied by definite radiologic evidence (bone scintigraphy, computed tomography or magnetic resonance). Patients with chronic bone disease, malignant diseases or autoimmune spondyloarthropathies were excluded.
Analysis of epidemiologic and clinical features was performed, including age, gender, overall status, signs and symptoms, laboratory tests [leukocyte count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and platelets], imaging techniques, treatment and outcome. Blood culture was performed in all patients before beginning antibiotics. Toxic appearance was defined as poor general condition, impaired perfusion, hypotension or tachycardia.
Follow-up of cases was done by phone questionnaires and included the presence of any musculoskeletal complaints or sequelae of PSI.
RESULTS
A total of 510 patients were diagnosed with OAI in any location during the study period, 265 of whom with septic arthritis. An initial diagnosis of isolated sacroiliitis was established in 29 patients, with 5 cases being inflammatory spondiloarthropathy. Therefore, infectious etiology was considered in the remaining 24 patients (4.7%), being 9% of the total SA. Four children were over 4 years old (3 caused by S. aureus). Thus, 20 patients under 4 years of age were studied and comprise the final sample, being the aim of this study. Although no etiologic agent was identified in any of these 20 cases, the clinical, laboratory, radiologic findings and the good response to antibiotic therapy led us to classify them as PSI.
The sample included 11 males and 9 females. The median age at diagnosis was 15 months, interquartile range (IQR) 12.2–27.5 months, 15 (75%) of whom being under 2 years old. The median duration of symptoms before being admitted to hospital was 4 days (IQR 2–6 days). None of them had toxic appearance. Fourteen patients (70%) reported fever at some point during the clinical course (median 38°C, IQR 38.2–38.6°C). A previous infection was identified in 11/20 cases (55%): 8 children with upper respiratory tract infection, 2 with gastroenteritis and 1 with stomatitis. No other predisposing events were identified.
The most frequent symptoms at clinical onset were refusal to sit without nuchal stiffness in 9 cases (45%); limp and irritability in 7 cases, respectively (35%); refusal to bear weight on the affected limb in 5 (25%) and night crying associated with spontaneously moving in bed in 4 cases (20%). ESR median value was 60 mm/h (IQR 40–82 mm/h), being above 20 mm/h in 17/19 patients (89 %), and CRP was higher than 20 mg/L (median of 25, IQR 10–58 mg/L) in 10/17 children (58%). All patients had mild or moderate thrombocytosis (median 445,000/µL; IQR 374,000–606,000/µL). Blood cultures were negative in all patients. All patients had a good response to medical treatment thus no surgery was needed; therefore, bone or synovial fluid samples were not obtained.
Plain radiographs of pelvis, lumbar spine or sacroiliac joints were done in 17/20 cases, with no abnormal findings in all cases. Bone scintigraphy was performed in 19 patients, leading to diagnostic confirmation in all of them, as well as magnetic resonance imaging in one case.
Thirteen patients (65%) were admitted, receiving intravenous antibiotherapy (median length of stay and intravenous therapy 3 days, IQR = 3–4.75 days). The patients were hospitalized for different reasons: intense irritability in 3 cases, gastroenteritis with poor oral tolerance in another case, 1 was admitted directly from the emergency department and the remaining ones corresponded to patients with a diagnosis prior to 2008, the year in which we began admitting only those patients who associated alarm data or with whom it was impossible to start oral treatment from the beginning. Intravenous cefuroxime was used in 7 patients (53%), cefotaxime in 3 (23%), clavulanic amoxicillin in 2 (15%) and clindamycin in 1 (7%). The remaining patients received entirely oral antibiotic treatment, even before blood cultures results, with cefuroxime axetil being the choice in 17 (85%) cases, amoxicillin clavulanate in 2 (10%) and clindamycin in 1 (5%). The median duration of antibiotic therapy was 28 days (IQR = 21–28 days). A complete resolution of symptoms was achieved in all patients. Thus, a changing antibiotics regimen was not necessary in any case. No patients developed any sequelae after at least 1 year of follow-up in clinical reviews. Analytical control was obtained in all cases when antibiotherapy was concluded with normalization of inflammatory parameters.
DISCUSSION
PSI is an uncommon disease in children and the literature is limited to small series of patients or isolated clinical cases. This is the largest single-center series of patients less than 4 years of age.
Since Schaad et al7 performed a review of patients published in the literature in 1980 including a total of 77 cases of PSI in <17 years of age, only a very few series have been published (Table 1). Two series have highlighted the subtle presentation of PSI in young children compared with the most recognizable clinical characteristics in older children. Donzelli et al2 included 16 children less than 15 years of age, dividing them into two groups by age: infants (6 months–4 years) and children–adolescents (4–16 years). The results obtained in the older group indicated higher CRP and ESR in the initial analysis as well as a higher rate of positivity in both blood cultures and joint fluid. In addition, Lavi et al3 describe 18 children under 16 years diagnosed of sacroiliitis differentiating two subgroups according to their age: 13 infants and toddlers (range 7–26 months) versus 5 older children (range 6–16 years). Their findings showed that in the group of older children, there was a higher positive blood culture rate, greater neutrophilia, more complications and greater need for intravenous treatment time. In comparison, infants presented a mild clinical course and fast recovery.
The prevalence of PSI in our series was 9% of SA, higher than traditionally described (1%–2%),7,8 probably because the large number of patients annually diagnosed with OAI in our hospital allows us to have a prompt clinical suspicion. It is slightly more frequency in males as described in previous studies (Table 1) and diagnostic delay was low, being less than 7 days in all cases in spite of the nonspecificity of the symptomatology.. Although adolescents and/or adults are able to accurately complain about gluteal pain and generally have a positive Faber test, toddlers and preschoolers may manifest imprecise symptoms which are usually unspecific, as described by Lavi et al,3 including irritability, limp, refusal to walk or sit or, while sitting, lifting a buttock in a characteristic way to avoid ipsilateral pain. This clinical presentation can lead to misdiagnosis with other processes such as appendicitis or hip arthritis.2,9 Moreover, meningeal signs can be difficult to assess.2 Bone scintigraphy has been described as a sensitive imaging modality in the assessment of pediatric patients with back pain.13 In our study, it was a useful technique in most patients showing 95% positive image rates, higher than previously described by Donzelli et al,2 but similar to the Alkhawaldeh data.13
Unlike older children, in whom sacroiliitis with fever and elevation of acute phase reactants may be the onset of arthritis-related juvenile idiopathic arthritis, in children under 4 years it is generally attributed to infectious etiology; although a pathogen is often not isolated. The global positive blood cultures rate described by different authors for PSI in pediatric patients is not high (31%–57%),2,10 being S. aureus, the most frequent causal microorganism identified.11,12 However, in our experience, it is usually seen in patients older than 4 years as happened in 3 of the 4 patients in our global series of PSI. In fact, S. aureus was identified as a causal agent only in 2 patients below 4 years in the series of patients reviewed (Table 1). As expected, sterile blood cultures were found in all of the younger patients in our series. This could probably be explained by the increasing involvement of K. kingae in OAIs in children below 4 years described over the past decades.5 Recently, Arcângelo et al4 have published a series of 6 patients diagnosed with sacroiliitis, 3 of whom were under 4 years of age, attributing two cases to K. kingae after obtaining a positive specific (polymerase chain reaction) in oropharynx. A limitation of our study is that this test was not available and thus not performed in any patient of our series. Although specific guidelines for the treatment of PSI have not been developed, 4–6 weeks courses have been described.3,9 Following the recent trends regarding the therapeutic approach to septic arthritis,14 a short course (during 2–4 days) of intravenous administration followed by a quick step to oral antibiotics may be suitable in PSI patients. Besides, Molinos et al9 reported a series of 11 PSI patients, of whom 2 received just oral antibiotic therapy due to different reasons with a favorable outcome. Our group has described that exclusively oral treatment could be a safe option in the youngest patients with good general condition, in whom K. kingae is suspected as the causative agent, and who can be closely followed as outpatients.6 When S. aureus is suspected, intravenous treatment is recommended following the conventional therapeutic management.14
In conclusion, even on the basis of a small retrospective series, we may emphasize that a high index of suspicion is necessary to establish an early diagnosis of pyogenic sacroiliitis in pediatric age, especially in younger patients in whom clinical and analytical data as well as physical examination may be more nonspecific.
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