1) A 5-year-old girl presented with sudden onset calf pain and difficulty walking after 3 days of fever. She was initially diagnosed with benign acute childhood myositis due to elevated creatine kinase levels. 2) The next day, she developed a rash and a positive dengue IgM test confirmed she had dengue fever. 3) Despite dengue being common in Malaysia, this is a rare reported case of myositis (calf muscle inflammation and pain) as an unusual presentation of dengue infection.

1. SOUTHEAST ASIAN J TROP MED PUBLIC H EALTH
CASE REPORT
MYALGIA CRURIS EPIDEMICA: AN UNUSUAL PRESENTATION
OF DENGUE FEVER
Rashidi Ahmad 1, Abdul Kursi Abdul Latiff 1 and Salmi Abdul Razak 2
1
Department of Emergency Medicine, 2Department of Pediatric, School of Medical Sciences,
University Science of Malaysia, Health Campus, Kubang Kerian, Kelantan, Malaysia
Abstract. We describe a 5-year-old girl who had sudden onset difficulty in walking after 3 days of
febrile illness. In the emergency department her creatine kinase level was elevated but urine
myoglobin was normal. She was diagnosed as having benign acute childhood myositis. Be-
cause of poor oral intake and dehydration, she was admitted to the pediatric ward. The next day
she had a petechial rash over the antecubital fossa, and dengue IgM back was positive. She was
treated conservatively and recovered uneventfully. Despite dengue fever being endemic in Ma-
laysia, this is the first case report of myositis following dengue infection in Malaysia.
INTRODUCTION is a well-described entity. This syndrome is
also known as benign acute childhood myo-
In 1957, Lundberg published the first re- sitis (BACM) and is self limited. Normally pa-
port on “Myalgia Cruris Epidemica” (Hussin et tients with BACM will be discharged with
al, 2003). This syndrome of muscle pain is medications and proper instructions. However,
characterized by sudden onset calf pain after “Myalgia Cruris Epidemica” is a rare manifes-
a period of rest and refusal to walk following tation of dengue infection, of which hemor-
viral illness (Rennie et al, 2005). It has been rhagic shock is one of the life threatening com-
suggested that calf pain causes the weakness plications. We report a preschool girl who pre-
instead of true inability to generate power. The sented to the emergency department with
majority of children have an elevated creatine muscle pain and difficulty in walking who was
kinase (CK). Leukopenia, thrombocytopenia initially diagnosed as having benign acute
and elevated serum glutamic oxaloacetic tran- childhood myositis, but later she was con-
saminase (SGOT) are less consistent labora- firmed to having dengue infection.
tory findings. Neurological examination has
been reported as normal (Rennie et al, 2005).
CASE REPORT
“Myalgia Cruris Epidemica” predominantly
affects school age children and typically oc- A 5-year-old girl was brought to the emer-
curs in boys (Lundberg, 1957). Myositis and gency department because of sudden onset
rhabdomyolysis associated with viral infection difficulty in walking. She was apparently well
until 3 days previoulsy when she developed a
Correspondence: A Rashidi, Department of Emer- high-grade fever, but had no chills or rigors.
gency Medicine, School of Medical Sciences, The fever decreased temporarily after taking
Health Campus, 16150 Kubang Kerian, Kelantan, paracetamol syrup. At the same time she had
Malaysia. lethargy and loss of appetite. She denied any
E-mail: shidee_ahmad@yahoo.com respiratory tract symptoms, headache, retro-
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2. M YALGIA CRURIS E PIDEMICA IN DENGUE INFECTION
orbital pain or joint pain. On the morning prior right antecubital fossa. A Pan Bio Rapid test
to admission, she developed bilateral calf pain (immunochromatography method) for dengue
which was dull and aching in nature. The pain was sent. Her dengue serology for IgM was
was aggravated by movement and relieved by positive while the IgG was negative. During
rest. There was no swelling or discoloration hospitalization the fever subsided, her plate-
of the calf muscles. Late afternoon, after she let count increased and she began to walk
woke up from her nap, she developed pro- again. She was discharged on the 4th day of
gressive muscle weakness of the lower ex- hospitalization after two sets platelet counts
tremities associated with difficulty in walking. were more than 100,000/mm3 and the creat-
She denied difficulty in breathing, double vi- ine kinase level was normal (45 IU/l).
sion, vomiting, diarrhea, or urinary symptoms.
Her family and medical history were unremark- DISCUSSION
able.
Dengue is the most common arthropod
On presentation, she appeared weak, but
borne arboviral infection in the world today. In
alert. Her pulse was 90 beats/minute and
Malaysia, the disease is endemically transmit-
regular rhythm, her blood pressure was 90/
ted by both Aedes aegypti and Aedes
60 mmHg, her respiratory rate was 26 breaths/
albopictus (Wallace et al, 1980; Rebecca,
minute, and she was febrile (38.5ºC). Her hy-
1992).
dration status was normal. She had no rashes,
pallor or jaundice. Cardiopulmonary and neu- It is estimated that there are at least 100
rological examinations were unremarkable. million cases of dengue fever (DF) annually,
Both her calves were warm and tender on ac- and 500,000 cases of dengue hemorrhagic
tive stretching. There was no discoloration or fever (DHF) require hospitalization. In Malay-
swelling of the calf muscles, fasciculations, sia, it has become a major public health prob-
myoclonus, or muscular atrophy observed. lem (Hussin et al, 2003).
Examination of gait revealed an unsteady, The clinical features of dengue fever vary
broad-based gait. The remainder of the physi- according to age of the patient. Infants and
cal examination was normal. The presentation young children usually have a febrile illness
of fever with inflammation of the calf muscles with a maculopapular rash and older children
made acute viral myositis the most likely di- have a mild febrile illness or the classic inca-
agnosis. pacitating disease, with abrupt onset, high
Her electrocardiogram showed no abnor- fever, severe headache, pain behind the eyes,
malities. Her complete blood count showed muscle pains, joint pains and rash (WHO,
white blood cells of 3,100/mm3 and platelets 2002). Some authors have reported atypical
of 92,000/mm 3. Her CK was markedly el- presentations of dengue virus infection, such
evated (1,400 IU/l), however, urine for myo- as mononeuropathies, encephalitis, cardiomy-
globinuria was negative. Serum biochemistries opathy or rhabdomyolysis (Solomon et al,
were normal. These findings are consistent 2000; Gibbon and Vaughn, 2002).
with benign acute childhood myositis. She was According to the WHO (Mackay et al,
admitted to the pediatric ward for further 1999), classic dengue fever is considered as
evaluation and treatment. a diagnosis if the patient presents with an
In the ward, she was treated conserva- acute febrile illness and two or more of the
tively with intravenous fluid and paracetamol following: headaches, retro-orbital pain, my-
250 mg every 4 hours. The next day the man- algia, athralgia, rash, hemorrhagic manifesta-
aging team noted a petechial rash over the tions and leukopenia. Those patients need to
Vol 38 No. 6 November 2007 1085

3. SOUTHEAST ASIAN J TROP MED PUBLIC H EALTH
be notified to the local health authorities even infection (Elisa PAN BIO) in 8 (25%) and sec-
before serology is known for preventive mea- ondary infection in 12 (30%). According to few
sures. study, there were two possible mechanisms
In this case, our patient presented with a for this: direct invasion of the muscle fibers
typical viral syndrome but the absence of other and release of myotoxic cytokines by the den-
features of dengue fever. Therefore, the initial gue virus, or myotoxic cytokines, particularly
diagnosis made for her illness was benign tumor necrosis factor (TNF), injured the af-
acute childhood myositis secondary to viral in- fected muscle. (Greco et al, 1977; Pratt et al,
fection. 1995; Seibold et al, 1998; Gagnon et al, 2002).
However, we could not explain why it mainly
Many viruses may cause a single episode affects the calf muscles.
of myositis and are unlikely to be recurrent.
Our patient developed petechial rashes
The most commonly reported infection is in-
on the 5th day of the febrile episode, which
fluenza B virus. Other viruses include influenza
turned out to be dengue virus infection. Be-
A, parainfluenza viruses 2 and 3, echoviruses
ing a country that is endemic for dengue in-
6 and 9, coxsakievirus, rotavirus, measles,
fection, we recommend reviewing classic
mumps, rubella, adenoviruses and viruses of
BACM patients in the outpatient department,
the herpes group (Rebecca, 1992; Rennie et
following up for at least a week. If dengue fe-
al, 2005).
ver can be ruled out, it is advisable to review
It is important for emergency department the patient after a couple of weeks to ensure
physicians to distinguish benign acute child- complete resolution of symptoms.
hood myositis from other more severe ill- We found little local medical literature re-
nesses. If patients present with classical signs garding this unusual presentation of dengue
of BACM, the physicians should feel comfort- infection. In a study by Horvath et al (1999),
able discharging them with medications but they reviewed 100 hospitalized dengue pa-
have them follow up. However, emergency de- tients in North Queensland from 1997 to 1999.
partment physicians need to look for features They found musculoskeletal pain, headache,
not associated with BACM, because some gastrointestinal symptoms, and nausea were
potentially life threatening diseases may mimic common, 99, 95, 95 and 92%, respectively.
BACM, such as dengue fever and Guillain Creatine kinase levels were measured in 15
Barre Syndrome. A thorough clinical history patients; 6 patients had elevated plasma cre-
and physical examination, especially neuro- atine kinase levels (NR <200 U/l). They con-
logical examination, and blood investigations, cluded that the high prevalence of elevated
such as full blood count, and biochemistry CK levels in the small group tested suggests
investigations, particularly CK, urine myoglo- that myositis was common in this outbreak of
bin, and viral serology, should be performed dengue fever. This is no great surprise since
in order to rule out the above matter. Failing musculo-skeletal symptoms are common.
to differentiate between BACM and possible Therefore, we postulate that myalgia cruris
life threatening events may lead to inappro- epidemica in dengue infection is under-re-
priate management and jeopardize the ported. In highlighting this condition, we hope
patient’s life. that more CK levels, urine myoglobin and vi-
A series of patients with BACM (Rajajee ral studies will be performed in future cases.
et al, 2005) was reported for Kanchi Kamakoti In conclusion, by reporting this case we
CHILDS Trust Hospital, Chennai, India. Sero- hope to raise awareness of unusual presen-
logical tests were positive for primary dengue tations of dengue (myalgia cruris epidemica)
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4. M YALGIA CRURIS E PIDEMICA IN DENGUE INFECTION
among healthcare providers as the incidence clinical features. Neurology 1999; 53: 21-7.
of dengue infection increases. Emergency Pratt RD, Bradley JS, Loubert E, et al. Rhabdo-
department physicians need to differentiate myolysis associated with acute varicella infec-
myalgia cruris epidemica of self limiting clas- tion. Clin Infect Dis 1995; 20: 450-3.
sical BACM from myalgia cruris epidemica of Rajajee S, Ezhilarasi S, Rajarajan K. Benign acute
dengue and Guillain Barre Syndrome, as the childhood myositis. Indian J Pediatr 2005; 72:
latter is a potentially life threatening condition. 399-400.
Rebecca George. Current status of the knowledge
of dengue/DHF/DSS in Malaysia: Clinical as-
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