Forum for Nordic Dermato-Venereology Nr 2, 2018 | Page 23

Carsten Suer Mikkelsen, Peter Bjerring, Kristian Bakke Arvesen and Daniel A. McDermott – Benign Acute Childhood Myositis (BACM) –
two incidents in the same patient
also affecting the extremities. It disappeared after 2–3 days.
The exanthema worsened by heat exposure. The cutaneous
manifestations were characteristic for an infection caused by
Parvovirus B19. There was no family history of neuromuscu-
lar diseases. The child had followed the normal vaccination
programme according to the recommendation for children
in Denmark. The family was 3 weeks earlier in Dubai and
the same year in Israel but without any signs of disease. The
child had no previous trauma(-s) and no extremely physical
activities or any other symptoms from the lower extremities.
There was no history of anuria or discoloration of the urine.
The pediatrician who performed the physical examination
found no signs of any trauma of the lower extremities. Neu-
rological examination showed normal sensitivity, normal
reflexes and normal strength of all muscle groups in the lower
extremities. Bilateral pain by palpation of the mm. gastroc-
nemii and mm solei was found, without any other signs of
abnormality. Blood test showed significant elevated creatine
kinase (CK): 3,197 U/l (33–200 U/l), but normal myoglobulin.
Aspartate aminotransferase (AST) was 179 U/l (15–37 U/l) and
C-reactive protein (CRP) normal (<0.20 mg/l). Potassium 5,5
mmol/l (3.5–5.1 mmol/l). Urine analysis normal, especially no
myoglobinuria or hematuria. Throat – and nose swabs were
normal. Blood tests were negative for Hemophilus Influenza
A and B. Tests for adenovirus, enterovirus, RSV-virus and
mycoplasma pneumonia were all negative.
The pain in both calfs disappeared completely 3 days after
start. The patient was treated with low dosage of NSAID and
paracetamol. The child was recommended rest and intake of
lots of water. During the whole period the child had normal
frequency of urination and no discolouration. Day 3 after the
first blood test a reduction of CK (1,550 U/l) was observed.
Two years later, in January 2017, the child developed a new
incident of BACM with the same neulogical symptoms and
significant increase of CK (3,317 U/l). Myoglobulin was
normal. This time she was diagnosed with Influenza type B
as being the cause of BACM. In between the two described
incidents she had multiple attacks with involuntary tics. Neu-
rological physical examination was normal and EEG showed
no abnormality.
Discussion
It is unknown if BACM is caused by a virus itself or by the
immunological response to the virus. Maybe the condition
Forum for Nord Derm Ven 2018, Vol. 28, No. 2
develops in early childhood as a age-related response to a
virus infection. Why it is more common in boys is unknown.
Theories suggest a genetic predisposition or an unknown
metabolic defect. The diagnosis of BACM is based on pain
in both calf muscles, normal strenght of the muscles, intact
reflexes, and increased CK.
The etiology of developing BACM is a virus and most com-
monly Hemophilus Influenzae A or B. Other infectious agents
described in case reports are: Parainfluenza, Enterovirus,
Adenovirus, Measles, Parotitis or Mycoplasma Pneumoniae
(3). Often the pain develops after resting and sleep. (4). The
majority of patients with BACM have significantly increased
CK (5). In previous reports we only found a few case reports de-
scribing histology showing segmental rhabdomyolysis and/or
moderate