CASE REPORT:
A 53-year-old man presented with severe pain and soreness in his left
upper arm. The pain started 2 days after the first dose of the ChAdOx1
nCoV-19 Corona Virus vaccine into his left deltoid muscle. The pain
initially developed in the left upper arm, followed by the right upper
arm and bilateral calf muscles (left more than right). The pain
gradually increased, and he had difficulty walking and moving his left
arm at the time of presentation. He also reported generalised muscle
weakness, more pronounced in the proximal upper and lower limbs than the
distal ones. There was no history of heavy manual labour or vigorous
exercise before the onset of symptoms. There was no malaise or fever.
There was no history of any skin rash, breathlessness, dry cough or
joint pain. He was non-diabetic and non-hypertensive, with no history of
any connective tissue disorders or allergic reactions to drugs or
vaccines. There has been no evidence of COVID-19 infection in the past.
On local examination, there was no swelling or erythema. There was
tenderness over the left deltoid muscle and bilateral calf muscles, more
so on the left side. The MMT score for the left deltoid muscle and left
calf muscles was 3/5, and for the same muscles on the right side it was
5/5.
Serologic testing yielded mildly
increased serum creatine kinase (187 U/L, reference range 40 – 171 U/L)
and alanine transaminase (50 U/L, reference range 10 – 40 U/L)
concentrations. Urine analysis excluded myoglobinuria. Initial
laboratory findings are summarised in Table 1.
Suspecting skeletal muscle damage, MRI of all the limbs was suggested.
At MRI, there was edema in the left deltoid muscle with a thin layer of
subfascial fluid adjacent to the muscle belly (Insert Figure 1). Deltoid
muscle architecture was preserved. Subtle edema was also noted in the
medial head of the left gastrocnemius muscle, with the edema fluid
tracking along the intermuscular plane between the gastrocnemius and
soleus (Insert Figure 2). No collection or abscess was seen. MRI of the
right arm and leg was normal. Based on these findings, a diagnosis of
COVID-19 vaccine-associated myositis was made. EMG, muscle biopsy, and
immunological workup could not be done as the patient did not give
consent.
The patient was advised to rest and take nonsteroidal anti-inflammatory
drugs (NSAIDs) for 1 week. Steroids or IVIg were not given, as the
symptoms were relatively mild and the liver enzymes were not elevated.
On follow-up after 1 week, the pain and tenderness had reduced
considerably. The MMT score for the left deltoid muscle and left calf
muscle was 5/5. However, the difficulty in walking persisted. Repeat
serum creatine kinase after 5 weeks was normal (121 U/L, reference range
40 – 171 U/L). A repeat MRI was not done, as the patient significantly
improved after initial management. A timeline of the events following
vaccination is given in Table 2.