Acute disseminated encephalomyelitis after Rocky Mountain spotted fever

Development and validation of a novel detection method for Rickettsia rickettsii using a loop-mediated isothermal amplification assay

Introduction

Rickettsia rickettsii is an obligate, intracellular pathogen and the causative agent of Rocky Mountain spotted fever (RMSF). RMSF is an important zoonotic disease due to its high fatal outcome in humans. The difficulty of clinical diagnosis due to the low sensitivity and specificity of current diagnostic methods are a principal setback. We reported the development of a new method for the detection of R. rickettsii in human and tick DNA samples using loop-mediated isothermal amplification (LAMP), as well as the validation of the LAMP test for R. rickettsii in field samples of infected ticks and humans, determining the diagnostic sensitivity and specificity, as well as the reproducibility of the test.

Methods

This technique uses hydroxy naphthol blue (HNB) as an indicator of the formation of magnesium pyrophosphate, a marker for the presence of DNA. Here, we used a putative R. rickettsii gene as a target for three pairs of primers that specifically amplify R. rickettsii DNA by hairpin-based isothermal amplification technique (LAMP).

Results and discussion

The sensitivity of the assay was ~1.6-3 pg, which is 10 times more sensitive than PCR. To determine the diagnostics specificity and sensitivity, 103 human DNA samples and 30 tick DNA samples were evaluated. For the human samples, a sensitivity for HNB of 93%, a specificity of 70% and a k of 0.53 were obtained. For electrophoresis the sensitivity was 97% with a specificity of 58% and a k of 0.42. For tick samples, a sensitivity of 80% was obtained, a specificity of 93% for HNB and for electrophoresis the sensitivity and specificity were 87%. The k for both was 0.73. The degree of concordance between HNB and electrophoresis was 0.82 for humans and for ticks, it was 0.87. The result is obtained in shorter time, compared to a PCR protocol, and is visually interpreted by the color change. Therefore, this method could be a reliable tool for the early diagnosis of rickettsiosis.

When to Think of Rickettsia

Rickettsiae are globally encountered pathogens with foci of endemicity and epidemic exacerbations under circumstances of crowding and decline of sanitation. Diagnosis is often missed due to misconceptions about epidemiology, confusing terminology and nonspecific clinical presentation. Rickettsioses should be considered in children with febrile illnesses exceeding the usual duration of a viral infection, in particular in children with rash, lymphadenopathy and nearly normal first-line laboratory tests, who reside in or return from endemic areas, recall a compatible contact history, have a constellation of symptoms starting after an arthropod bite, live under troubled social circumstances, or are part of a cluster of similar cases.

Persisting Rickettsia typhi Causes Fatal Central Nervous System Inflammation

Rickettsioses are emerging febrile diseases caused by obligate intracellular bacteria belonging to the family Rickettsiaceae. Rickettsia typhi belongs to the typhus group (TG) of this family and is the causative agent of endemic typhus, a disease that can be fatal. In the present study, we analyzed the course of R. typhi infection in C57BL/6 RAG1(-/-) mice. Although these mice lack adaptive immunity, they developed only mild and temporary symptoms of disease and survived R. typhi infection for a long period of time. To our surprise, 3 to 4 months after infection, C57BL/6 RAG1(-/-) mice suddenly developed lethal neurological disorders. Analysis of these mice at the time of death revealed high bacterial loads, predominantly in the brain. This was accompanied by a massive expansion of microglia and by neuronal cell death. Furthermore, high numbers of infiltrating CD11b(+) macrophages were detectable in the brain. In contrast to the microglia, these cells harbored R. typhi and showed an inflammatory phenotype, as indicated by inducible nitric oxide synthase (iNOS) expression, which was not observed in the periphery. Having shown that R. typhi persists in immunocompromised mice, we finally asked whether the bacteria are also able to persist in resistant C57BL/6 and BALB/c wild-type mice. Indeed, R. typhi could be recultivated from lung, spleen, and brain tissues from both strains even up to 1 year after infection. This is the first report demonstrating persistence and reappearance of R. typhi, mainly restricted to the central nervous system in immunocompromised mice.

Non-lyme tick-borne diseases: a neurological perspective

Tick-borne diseases are prevalent throughout the world and present a diagnostic challenge owing to their nonspecific clinical symptoms. Many tick-borne diseases involve the central and peripheral nervous systems. Early diagnosis or at least suspicion of a tick-borne cause is necessary to institute early empiric treatment. After a brief review of tick biology, we present the most common tick-borne diseases. A brief discussion of epidemiology, the transmission route, and pathogenesis is followed by a discussion of the clinical manifestations, diagnosis and treatment options when available. The review emphasizes the infectious causes with a significant neurological manifestation.

Acuted disseminated encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) is a disorder of the central nervous system (CNS) characterized by an acute event, typically with encephalopathy, in which diffuse CNS involvement occurs. It may follow an infectious event and occurs more commonly in young children. Pulse steroid treatment is frequently used to treat ADEM. Although ADEM is typically described as a benign condition, with children generally recovering motor function and resolution of lesions on magnetic resonance imaging (MRI), residual cognitive deficits may occur. This chapter aims to review the clinical features, typical presentation, differential diagnosis, treatment and prognosis of ADEM.

Probable acute disseminated encephalomyelitis due to Haemophilus influenzae meningitis

We report the case of a 17-year-old male on long-term steroid therapy for minimal lesion glomerulopathy who, after an upper respiratory infection, presented with Haemophilus influenzae type b meningitis. Twenty-four hours later he developed depression of consciousness which progressed to coma and left hemiparesis. Brain magnetic resonance imaging (MRI) revealed multiple lesions (hyperintense on T2 and slightly hypointense on Tl) involving mainly white matter suggestive of inflammation. MRI features were compatible with acute disseminated encephalomyelitis (ADEM), although a differential diagnosis included cerebritis or vasculitis, secondary to bacterial meningitis. The patient was treated with high-dose steroids which resulted in a gradual improvement followed by complete clinical recovery. We propose a diagnosis of ADEM was the best diagnosis because of the radiological features and response to steroids. The occurrence of ADEM associated with acute meningitis, however rare, represents an important diagnostic challenge for the clinician.

Rocky Mountain spotted fever

Rocky Mountain spotted fever (RMSF) is an unusual but important dermatological condition to identify without hesitation. The classic triad of headache, fever, and a rash that begins on the extremities and travels proximally to involve the trunk is found in a majority of patients. The cutaneous centripetal pattern is a result of cell to cell migration by the causative organism Rickettsia rickettsii. Such individuals should receive prompt antimicrobial therapy and supportive care to avoid serious and potentially fatal complications.

[Acute disseminated encephalomyelitis. Pathogenesis, diagnosis, treatment, and prognosis]

Acute disseminated encephalomyelitis (ADEM) is typically a monophasic, demyelinating disease of the CNS that predominantly affects children. Typically, its clinical symptoms follow an infection or vaccination. In this regard, numerous viral and bacterial pathogens as well as several vaccinations have been associated with ADEM. Studies from animal models suggest that primary and secondary autoimmune responses may contribute to CNS inflammation and demyelination in ADEM. The diagnosis of ADEM is strongly suggested by a close temporal relationship between a viral infection or immunization and the onset of neurologic symptoms, and it is supported by extensive, multifocal, subcortical white-matter disease on brain magnetic resonance imaging. While mild lymphocytic pleocytosis and elevated proteins are detectable in the CSF in ADEM, oligoclonal bands are not always present. Treatment of this disorder consists of anti-inflammatory and immunosuppressive therapies, and the prognosis is generally considered favorable.

Acute disseminated encephalomyelitis in childhood: epidemiologic, clinical and laboratory features

BACKGROUND

Acute disseminated encephalomyelitis (ADEM) is a central nervous system demyelinating disease that usually follows an apparently benign infection in otherwise healthy young persons. The epidemiology, infectious antecedents and pathogenesis of ADEM are poorly characterized, and some ADEM patients are subsequently diagnosed with multiple sclerosis (MS).

METHODS

We retrospectively (1991-1998) and prospectively (1998-2000) studied all persons aged < 20 years diagnosed with ADEM from the 3 principal pediatric hospitals in San Diego County, CA, during 1991-2000. Acute neurologic abnormalities and imaging evidence of demyelination were required for study inclusion. Epidemiologic variables, risk factors, clinical course, laboratory and radiographic findings, neuropathology and treatment data were analyzed. Interleukin (IL)-12, interferon-gamma (IFN-gamma) and IL-10 were assayed in blinded manner on cerebrospinal fluid (CSF) obtained prospectively from a subset of ADEM cases and compared with CSF from patients with enteroviral (EV) meningoencephalitis confirmed by polymerase chain reaction (PCR) and controls without pleocytosis.

RESULTS

Data were analyzed on 42 children and adolescents diagnosed with ADEM during 1991-2000, and CSF IL-12, IFN-gamma and IL-10 levels were compared among ADEM (n = 14), EV meningoencephalitis (n = 14) and controls without pleocytosis (n = 28). Overall incidence of ADEM was 0.4/100,000/year; incidence quadrupled during 1998-2000 compared with earlier years. No gender, age stratum, ethnic group or geographic area was disproportionately affected. A total of 4 (9.5%) patients initially diagnosed with ADEM were subsequently diagnosed with MS after multiple episodes of demyelination. Although most children eventually recovered, 2 died, including 1 of the 3 ultimately diagnosed with MS. Magnetic resonance imaging was required for diagnosis among 74% of patients; computerized tomography findings were usually normal. Patients with EV had significantly higher mean CSF IFN-gamma (P = 0.005) and IL-10 (P = 0.05) than patients with ADEM and controls without CSF pleocytosis. CSF from ADEM patients had CSF cytokine values statistically similar to those of 3 patients subsequently diagnosed with MS.

CONCLUSIONS

ADEM is a potentially severe demyelinating disorder likely to be increasingly diagnosed as more magnetic resonance imaging studies are performed on patients with acute encephalopathy. Further characterization of the central nervous system inflammatory response will be needed to understand ADEM pathogenesis, to improve diagnostic and treatment strategies and to distinguish ADEM from MS.

Acute disseminated encephalomyelitis: a review of 18 cases in childhood

OBJECTIVE

Acute disseminated encephalomyelitis (ADEM) is a treatable inflammatory demyelinating disorder seen more commonly in children than in adults. It typically presents to general paediatricians, often, like encephalitis, with non-specific cerebrospinal fluid findings. The brain computerized tomography scan is usually normal, so is falsely reassuring and delays the diagnosis, which might result in considerable morbidity. The present study was initiated to report on the various modes of presentation and raise the awareness of the diagnosis of ADEM among general paediatricians.

METHODS

A retrospective review of the case notes of 18 children with a diagnosis of ADEM established in a tertiary referral centre from 1995 to 2000 was undertaken with particular reference to clinical features, investigations and treatment.

RESULTS

The most common presenting features were ataxia (10 cases), followed by headache (eight cases) and weakness (five cases). Magnetic resonance imaging (MRI) of the brain was needed to confirm the diagnosis in all 18 children. Treatment usually included a course of intravenous methylprednisolone followed by a tapering dose of oral prednisolone over several weeks. Although the outcome for most of the children was generally good, two relapsed after cessation of steroids and five children had ongoing disabilities.

CONCLUSIONS

The investigation of choice for establishing the diagnosis of ADEM was MRI of the brain. Other investigations were seldom helpful in reaching the diagnosis. Early diagnosis and prompt treatment of ADEM will probably reduce morbidity.

Acute disseminated encephalomyelitis: recognition in the hands of general paediatricians

Acute disseminated encephalomyelitis will often present to the general paediatrician as an acute polysymptomatic encephalopathy, and initially the diagnosis may not be clear. A brain MRI scan is essential in establishing the diagnosis and so enabling appropriate advice and treatment to be given. Multicentre clinical audit of outcome and controlled therapeutic trials are needed to secure an evidence base for current practice.

Acute disseminated encephalomyelitis in children

OBJECTIVE

To describe the epidemiologic, clinical, neuroimaging, and laboratory features; treatment; and outcome in a cohort of children with acute disseminated encephalomyelitis (ADEM).

METHODS

A 6-year retrospective chart review of children with the diagnosis of ADEM was conducted.

RESULTS

Eighteen cases were identified. Sixteen patients (88%) presented in either winter or spring. Thirteen children (72%) had a recent upper respiratory tract illness. Patients presented most often with motor deficits (77%) and secondly with altered consciousness (45%). Spinal fluid abnormalities occurred in 70%. Despite rigorous microbiologic testing, a definite microbiologic diagnosis was established only in 1 child with Epstein-Barr virus disease and probable or possible diagnoses in 3 children with Bartonella henselae, Mycoplasma pneumoniae, or rotavirus disease. Brain magnetic resonance imaging identified lesions in the cerebral cortex in 80%, in subcortical white matter in 93%, in periventricular white matter in 60%, in deep gray matter in 47%, and in brainstem in 47% of patients. Eleven patients (61%) were treated with corticosteroids, and 2 were treated with intravenous immunoglobulins. All patients survived. Three patients (17%) had long-term neurologic sequelae.

CONCLUSIONS

Epidemiologic evidence from this study suggests an infectious cause for ADEM. The agent is most likely a difficult-to-diagnose winter/spring respiratory virus. Magnetic resonance imaging was the neuroimaging study of choice for establishing the diagnosis and for following the course of the disease. Prognosis for survival and outcome was excellent. Recurrent episodes of ADEM must be differentiated from multiple sclerosis.

Rickettsia typhi infection presenting as subacute meningitis

We report two children with Rickettsia typhi infection presenting with mild central nervous system manifestations and pleocytosis in cerebrospinal fluid. Murine typhus should be included in the differential diagnosis of meningoencephalitis in children who are residents of endemic areas.