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Revista chilena de pediatría

versión impresa ISSN 0370-4106

Rev. chil. pediatr. vol.88 no.2 Santiago abr. 2017

http://dx.doi.org/10.1016/j.rchipe.2016.07.002 

Clinical Case

 

Benign acute childhood myositis: Clinical series and literature review

Miositis aguda benigna de la infancia. Serie clínica y revisión de la literatura

 

Felipe Cavagnaro S.M.a, Alejandra Aird G.a, Ingrid Harwardt R.b, Carmen Gloria Marambio Q.a

aServicio de Pediatría, Clínica Alemana de Santiago y Facultad de Medicina Clínica Alemana-Universidad del Desarrollo. Santiago, Chile
bUnidad de Urgencia Pediátrica, Clínica Alemana de Santiago, Santiago, Chile

Correspondencia a:


Benign acute childhood myositis (BACM) is a rare clinical condition that mainly affects pre-school and school age-children. It is usually preceded by a viral illness, particularly influenza virus infection. Objective: To describe a cluster of BACM cases that were seen in a paediatric unit. Patients and Methods: A retrospective serie of cases that presented with a clinical picture suggestive of BACM between August and November 2012 in the paediatric emergency department of a private clinic. Results: Nine children, between 4 and 12 years, presented with a history of a recent febrile upper viral respiratory infection, followed by intense calf pain and claudication. They all recovered without complications. Laboratory results showed a marked increase in CK, with a mean of 4,066 IU/l. Three of the cases had influenza B infection and one Mycoplasma pneumonia infection. They were managed conservatively with hydration and non-steroidal anti-inflammatory drugs. Conclusions: BACM is a benign entity with a characteristic clinical presentation that can be managed most of the time in the ambulatory setting, avoiding invasive studies and unnecessary hospital admission.

Keywords: Viral myositis; Influenza; Limp; ChildrenIntroduction


 

Benign acute childhood myositis (BACM) is a transient and rare inflammatory condition. It occurs mainly in school and pre-school aged children, predominantly affects males, and case outbreaks are observed in periods of respiratory virus epidemics1–3. It is characterized by sudden and intense pain with marked increase of sensitivity of the calf muscles, to the point of hindering or impeding walking, or bearing weight. Laboratory tests include elevated creatine kinase (CK) muscle enzyme.

BACM is of self-limiting evolution, with an excellent prognosis and no functional sequelae2-7. It was initially described in Sweden in the late 1950s by Lundberg as epidemic cruris myalgia8. Since then, numerous sporadic cases and some outbreaks have been described around the world, but their actual prevalence is still unknown. The review by Buss et al.9 shows an incidence of 2.6 cases per 100,000 children under 18 years old in epidemic times and 0.23 cases in non-epidemic times. Only sporadic cases have been reported in adults.

The etiology of this condition strongly indicates a viral origin: influenza virus (A and B) is the most frequently reported2,4,5. The etiologic mechanism of myositis is still controversial. Current theories support damage by direct invasion of the virus into muscle tissue, with viral particles being isolated in biopsies of gastrocnemius of children with BACM4,7,10. The initial infection causes necrosis of the muscle fiber, which results in elevated CK. Muscular study has been performed infrequently, in view of the short duration of symptoms and the well-known good prognosis of this condition. The few reported muscle biopsies present normal myocytes, myositis4, segmental rhabdomyolysis11 or moderate muscle necrosis with interstitial inflammation12. When electromyographies have been performed, they have been normal or have shown patchy myopathic changes3.

The objective of this article is to describe the clinical experience in an outbreak of patients that came to our care center, in a short period of time, with clinical features suggestive of BACM. Along with analyzing the particularities of this series, we review the topic and the elements of clinical judgment for its appropriate diagnostic study and therapeutic management. According to our review of the literature, there is no other series of BACM cases published in Latin American countries.

Patients and Method

Retrospective clinical series of patients who consulted for a clinical picture compatible with BACM in the period between August 1 and November 30, 2012, in the pediatric emergency department of a private clinic in the Metropolitan Region, Santiago, Chile. All patients who had a history of known neuromuscular and immunological disease, active bacterial infections or who were taking drugs with possible muscle toxicity (eg statins) were excluded.

Clinical records of 9 patients were reviewed, emphasizing clinical presentation characteristics, diagnostic elements, therapeutic management and initial evolution..

This study has been approved by the Institutional Ethics Committee.

Results

In a 4-month period, 9 patients with BACM-compatible clinical presentation were presented. All of them with a recent history of severe acute pain in both calves and claudication. The distribution by gender was practically equivalent (5/9 males), with a mean age of 7.3 years (4-12 years). As a clinical antecedent, all patients presented a fever prodrome associated with upper respiratory symptoms. The average onset of muscle symptoms was 4.4 days (3-5 days) after the onset of respiratory symptoms (table 1).

The physical examination on admission showed all of them in good general condition, although a third remained still feverish. They all had severe localized pain in both calves, especially triggered by foot dorsiflexion or vigorous compression of the gastrocnemius muscles, with a greater or lesser degree of claudication: 2 did not walk, 2 had equine gait and one Frankenstein gait (table 1). Muscle strength, tone, and osteotendinous reflexes of the lower extremities were uniformly conserved. The remainder of the physical examination was normal, except for the presence of upper respiratory symptoms in all of them. Although all of our patients were evaluated by a pediatric neurologist, none merited extra studies to rule out any other differential diagnosis.

Table 1. Patients demographic characteristics, prodromal symptoms and presentation latency

Of the 9 patients, 8 were hospitalized for monitoring and study for a period of no more than 3 days. The clinical management consisted exclusively of hydration and nonsteroidal anti-inflammatory drugs, resulting in a favorable evolution in all of them

In our series, all patients evaluated with blood counts, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and CK levels. In the exams, leukopenia with neutropenia was noted in 6 of 9 patients. Four patients had mild thrombocytopenia and all had an increase in CK, with an average value of 4,066 IU/L (table 2). Both ESR and CRP were in the normal range in all of them. Transaminases were monitored in 8 patients; of these, 7 had a slight increase in their values, mainly glutamic oxalacetic transaminase (GOT), and 2 of them had a slight increase in lactate dehydrogenase (LDH).

Table 2. Physical Examination on admission

Eight of 9 patients were monitored for renal function with serum creatinine, all in the normal range. Myoglobinemia was requested in 5 patients: in 4 of them it was elevated (table 2), although all the urinalysis were normal and without myoglobinuria. The etiological study showed associated agents in only 4 of our patients: 3 patients with influenza B and one with Mycoplasma pneumoniae. In the rest, the search for etiological agent was negative (tabla 2).

Table 3. Laboratory investigations

Table 4. Creatinekinase values

Our patients evolved satisfactorily during hospitalization, with progressive drop in CK levels (figure 1), without complications and with a rapid regression of theirs symptomatology. In the 5 patients who had ambulatory follow up, the total resolution time of symptoms from discharge was not greater than 48 h (table 1).

Figure 1. Evolution of creatinkinase (CK) levels in blood.

It is interesting to mention that one of our male patients presented a new episode of BACM one year later, also associated with previous respiratory infection without etiologic study, which was managed on an outpatient basis.

Discussion

This report describes an outbreak of BACM that occurred in our care center, coinciding with a period of higher prevalence of respiratory infections, which has been related to an increase in the incidence of this condition8,13. The influenza virus (with predominance of influenza B) has been the most frequently involved1,2,4,5,14,15.However, association with other viruses such as coxsackie, adenovirus, parainfluenza, respiratory syncytial virus, among others, and bacteria such as Mycoplasma pneumoniae has been described3–5. In our series, we isolated the responsible agent in 4 patients (3 with influenza B and 1 with Mycoplasma pneumoniae). However, in most of the cases only direct immunofluorescence (DIF) and serological studies for Mycoplasma pneumoniae were available, which decreases the detection sensitivity. In our laboratory the sensitivity of the DIF for the different respiratory viruses is less than 50%, except for RSV, for which it reaches 63%.

All of our patients presented the classic clinical picture, with predominance of bilateral calf pain and claudication and with a febrile respiratory prodrome.. The age of presentation also coincided with that described in the literature2,4,6,8, although we did not find a clear male predilection, which could be explained by the small number of patients. Of the 2 types of gait described in BACM: a wide based, stiff legged gait (Frankenstein gait) and toe walking (gait in equine)4, both were observed in our series. The calf muscles invariably show excruciating pain on palpation and dorsiflexion of the foot, although, exceptionally, there is compromise of other muscle groups such as thighs, arms, back and neck7. At the time of diagnosis, and in agreement with our series, patients are usually afebrile, in good general conditions and with a normal neurological examination. If discrete muscle weakness is perceived it is due to pain and not to neurological deficit.

The most striking laboratory result is the marked elevation of the CK muscle enzyme (20-30 times higher than normal values) which typically normalizes in a couple of weeks4,5. Even in cases where CK has been massively elevated it is seldom associated with myoglobinuria and significant rhabdomyolysis16. Other findings are leucocytopenia with moderate neutropenia, thrombocytopenia and a mild and transient elevation of transaminases and LDH6,16,17. Inflammatory markers are generally normal, although ESR may be slightly increased2,4. This coincides with the laboratory parameters observed in our patient group.

The clinical evolution described in the literature is similar to that recorded by us, with a marked improvement at 24 h of evolution18. The process is self-limited with complete recovery between the third and tenth days, complications are infrequent and do not leave functional sequelae4,16. Acute renal failure secondary to myoglobinuria due to massive rhabdomyolysis is anecdotal in patients with BACM and has not been observed in our patients16,19. Recurrences are rare - just one case detected in our group - and caused by different viruses at each opportunity5,17. It has been shown serologically that children with myositis associated with influenza virus are susceptible to the strain involved, and those who presented a second episode did so with a strain different from that of the initial infection. This disorder appears to be present only at the first exposure to a particular virus, which may explain the few cases reported in adulthood7,17.

The symptoms of BCAM are alarming and can cause concern and confusion both in parents and health professionals. On the other hand, there is a wide differential diagnosis made up of a spectrum of diseases that present with claudication and/or muscle pain. These include infectious, muscular and neurological diseases such as acute myositis associated with other infectious diseases (eg dengue), toxic myoglobinuria, rhabdomyolysis, Guillain-Barré syndrome, ataxia, transverse myelitis, muscular dystrophies, polymyositis, juvenile dermatomyositis, trichinosis , osteomyelitis, arthritis and deep vein thrombosis, among others16,20,21.

However, the clinical presentation of BCAM is characteristic and musculoskeletal and neurological examination in these patients is normal, except for pain on palpation of the affected muscle group and discrete secondary weakness16.

Therefore, on suspicion of this entity, it is very important to obtain an exhaustive medical history and a detailed physical examination, where the musculoskeletal or neurological involvement suggestive of more ominous differential diagnoses is excluded. Findings that guide other diagnoses include: family history of neuromuscular disease, history of recent trauma, persistent high fever, dark urine, subacute or chronic progression, rash, frank muscle weakness or other neurological examination abnormalities16.

Laboratory tests should be dimensioned and oriented to establish the diagnosis (elevation of CK). Exceptionally, and on suspicion of rhabdomyolysis due to excessive CK increase, renal function could be monitored. However, it is important to be aware of this rare but severe complication, suggested by dark urine and positive blood on urine dipstick in the absence of red blood cells on microscopic examination of urine. An accurate diagnosis prevents invasive studies and unnecessary hospitalizations, while avoiding greater anxiety in the patient and his family.

Management of BCAM is symptomatic18,22. The use of antivirals in the case of influenza infection is of little benefit, since in most cases the acute respiratory infection is already in resolution1,20,21. Influenza vaccine has proven to reduce influenza complications, which could theoretically reduce the incidence of BCAM, which is not proven4,21.

This study has some limitations, such as the small number of patients included, which does not allow generalization of the conclusions. Likewise, as a retrospective study, data recording in the clinical file by the treating physicians was not done in a protocolized way, so it was not always complete. For this same reason, the clinical management of these patients was not necessarily uniform. Since the etiological study was performed in most cases with less sensitive tests than is currently available, there may have been an etiological underdiagnosis of our patients. Finally, we only have the follow-up data of those patients who were controlled in our outpatient clinic, which does not allow us to know with greater certainty eventual recurrences or long term complications.

Conclusion

Our work, besides presenting the clinical series, fulfills the objective of emphasizing that BCAM is a benign, self-limited entity with an excellent prognosis, with a characteristic clinical presentation and that in most cases it can be managed on an outpatient basis. For this reason, the study should be limited and oriented towards diagnostic confirmation, and avoid invasive studies and unnecessary hospitalizations.

 

References

1. Mall S, Buchholz U, Tibussek D, et al. A large outbreak of influenza B associated benign acute childhood myositis in Germany, 2007/2008. Pediatr Infect Dis J. 2011;30(8):e142-6.

2. Ferrarini A, Lava SA, Simonetti GD, Ramelli GP, Bianchetti M. Swiss Italian Society of Pediatrics. Influenza virus B-associated acute benign myalgia cruris: An outbreak report and review of the literature. Neuromuscular Disorders 2014; 24: 342-6.

3. Tippet E, Clark R. Benign acute childhood myositis following human parainfluenza virus type-1 infection. Emergency Medicine Australasia 2013;25: 248-51.

4. Mackay MT, Kornberg AJ, Shield LK, Dennett X. Benign acute childhood myositis. Laboratory and clinical features. Neurology 1999; 53: 2127-31.

5. Dietzman DE, Schaller JG, Schaller C, Ray G, Reed M. Acute myositis associated with influenza B infection. Pediatrics 1976;57:255-8.

6. Zafeiriou D, Katzos G, Gombakis N, Kontopoulos EE, Tsantali C. Clinical features, laboratory findings and differential diagnosis of benign acute childhood myositis. Acta Paediatr 2000; 89: 1493-4.

7. Agyeman P, Duppethaler A, Heininger U, et al. Influenza associated myositis in children. Infection 2004;32:199-203.

8. Lundberg A. Myalgia cruris epidémica. Acta Paediatr 1957;46: 18-31.

9. Buss BF, Shine VM, Safranek TJ, Uyeki TM. Pediatric influenza-associated myositis-Nebraska, 2001-2007. Influenza Other Respir Viruses 2009;3: 277-285.

10. Bove KE, Hilton PK, Partin J. Morphology of acute myopathy associated with influenza B infection. Pediatr Pathol 1983; 1:51-66.

11. Mejlszenkier JD, Safran AP, Healy JJ, et al. The myositis of influenza. Pediatrics 1977;60:761-2.

12. Ruff RL, Secrist D. Viral studies in benign acute childhood myositis. Arch. Neurol 1982;39: 261-3.

13. Middleton PJ, Alexander RM, Szymanski MT. Severe myositis during recovery from influenza. Lancet 1970;2:533-5.

14. Farrell MK, Partin JC, Bove KE. Epidemic influenza myopathy in Cincinnati in 1977. J Pediatr 1980;96:545-51.

15. Hu JJ, Kao CL, Lee PI, et al. Clinical features of influenza A and B in children and association with myositis. J Microbiol Immunol Infect 2004;37:95-8.

16. Jain S, Kolber MR. A stiff-legged gait: benign acute childhood myositis. CMAJ 2009;181:711-3.

17. Rennie LM, Hallam NF, Beattie TF. Benign acute childhood myositis in an accident and emergency setting. Emerg Med J 2005;22:686-8.

18. Neocleous C, Spanou C, Mpampalis E, et al. Unnecessary diagnostic investigations in benign acute childhood myositis: a case series report. Scott Med J 2012;57:1-3.

19. Mannix R, Tan ML, Wright R, Baskin M. Acute Pediatric Rhabdomyolysis: Causes and rates of renal failure. Pediatrics 2006;118:2119-2125.

20. Heiner JD, Ball VL. Clinical Communications: Pediatrics. A child with benign acute childhood myositis after influenza. J Emerg Med 2010;39:316-9.

21. Rodríguez E, Sabbaj L, Schargrodsky L. Miositis Benigna Aguda: una inusual causa de impotencia funcional en pediatría. Consultorios externos. Hospital de niños Dr. Ricardo Gutiérrez. Rev Hosp Niños BAires septiembre 2011;53: 162-6.

22. Cela de Julián ME; Martín Puerto MJ; Otero JR. Miositis viral aguda benigna: ni confirmación etiológica ni pruebas complementarias. An Esp Pediatr 1998;49:437-8.

___________________

Received: 9-3-2016; Accepted: 4-7-2016

Ethical Responsibilities

Human Beings and animals protection: Disclosure the authors state that the procedures were followed according to the Declaration of Helsinki and the World Medical Association regarding human experimentation developed for the medical community.

Data confidentiality: The authors state that they have followed the protocols of their Center and Local regulations on the publication of patient data.

Rights to privacy and informed consent: The authors have obtained the informed consent of the patients and/or subjects referred to in the article. This document is in the possession of the correspondence author.

Financial Disclosure

Authors state that no economic support has been associated with the present study.

Conflicts of Interest

Authors state that any conflict of interest exists regards the present study.

Acknowledgements

The authors thank Dr. Lorena Porte Torre for the information provided on the sensitivity and specificity of the respiratory immunofluorescence virus in our center.

Correspondencia a:

Felipe Cavagnaro S.M.

fcavagnaro@alemana.cl

1. Mall S, Buchholz U, Tibussek D, et al. A large outbreak of influenza B associated benign acute childhood myositis in Germany, 2007/2008. Pediatr Infect Dis J. 2011;30(8):e142-6.         [ Links ]

2. Ferrarini A, Lava SA, Simonetti GD, Ramelli GP, Bianchetti M. Swiss Italian Society of Pediatrics. Influenza virus B-associated acute benign myalgia cruris: An outbreak report and review of the literature. Neuromuscular Disorders 2014; 24: 342-6.         [ Links ]

3. Tippet E, Clark R. Benign acute childhood myositis following human parainfluenza virus type-1 infection. Emergency Medicine Australasia 2013;25: 248-51.         [ Links ]

4. Mackay MT, Kornberg AJ, Shield LK, Dennett X. Benign acute childhood myositis. Laboratory and clinical features. Neurology 1999; 53: 2127-31.         [ Links ]

5. Dietzman DE, Schaller JG, Schaller C, Ray G, Reed M. Acute myositis associated with influenza B infection. Pediatrics 1976;57:255-8.         [ Links ]

6. Zafeiriou D, Katzos G, Gombakis N, Kontopoulos EE, Tsantali C. Clinical features, laboratory findings and differential diagnosis of benign acute childhood myositis. Acta Paediatr 2000; 89: 1493-4.         [ Links ]

7. Agyeman P, Duppethaler A, Heininger U, et al. Influenza associated myositis in children. Infection 2004;32:199-203.         [ Links ]

8. Lundberg A. Myalgia cruris epidémica. Acta Paediatr 1957;46: 18-31.         [ Links ]

9. Buss BF, Shine VM, Safranek TJ, Uyeki TM. Pediatric influenza-associated myositis-Nebraska, 2001-2007. Influenza Other Respir Viruses 2009;3: 277-285.         [ Links ]

10. Bove KE, Hilton PK, Partin J. Morphology of acute myopathy associated with influenza B infection. Pediatr Pathol 1983; 1:51-66.         [ Links ]

11. Mejlszenkier JD, Safran AP, Healy JJ, et al. The myositis of influenza. Pediatrics 1977;60:761-2.         [ Links ]

12. Ruff RL, Secrist D. Viral studies in benign acute childhood myositis. Arch. Neurol 1982;39: 261-3.         [ Links ]

13. Middleton PJ, Alexander RM, Szymanski MT. Severe myositis during recovery from influenza. Lancet 1970;2:533-5.         [ Links ]

14. Farrell MK, Partin JC, Bove KE. Epidemic influenza myopathy in Cincinnati in 1977. J Pediatr 1980;96:545-51.         [ Links ]

15. Hu JJ, Kao CL, Lee PI, et al. Clinical features of influenza A and B in children and association with myositis. J Microbiol Immunol Infect 2004;37:95-8.         [ Links ]

16. Jain S, Kolber MR. A stiff-legged gait: benign acute childhood myositis. CMAJ 2009;181:711-3.         [ Links ]

17. Rennie LM, Hallam NF, Beattie TF. Benign acute childhood myositis in an accident and emergency setting. Emerg Med J 2005;22:686-8.         [ Links ]

18. Neocleous C, Spanou C, Mpampalis E, et al. Unnecessary diagnostic investigations in benign acute childhood myositis: a case series report. Scott Med J 2012;57:1-3.         [ Links ]

19. Mannix R, Tan ML, Wright R, Baskin M. Acute Pediatric Rhabdomyolysis: Causes and rates of renal failure. Pediatrics 2006;118:2119-2125.         [ Links ]

20. Heiner JD, Ball VL. Clinical Communications: Pediatrics. A child with benign acute childhood myositis after influenza. J Emerg Med 2010;39:316-9.         [ Links ]

21. Rodríguez E, Sabbaj L, Schargrodsky L. Miositis Benigna Aguda: una inusual causa de impotencia funcional en pediatría. Consultorios externos. Hospital de niños Dr. Ricardo Gutiérrez. Rev Hosp Niños BAires septiembre 2011;53: 162-6.         [ Links ]

22. Cela de Julián ME; Martín Puerto MJ; Otero JR. Miositis viral aguda benigna: ni confirmación etiológica ni pruebas complementarias. An Esp Pediatr 1998;49:437-8.         [ Links ]

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