Muscle weakness may, in rare cases, be a presenting symptom of ANCA-associated vasculitis, and a muscle biopsy should be considered in these cases to confirm a diagnosis, a case report suggests.
The report, “Muscle weakness as a presenting symptom in ANCA-associated vasculitis,” appeared in the European Journal of Rheumatology.
ANCA-associated vasculitis (AAV) usually involves the kidneys, lungs, skin, or nervous system, but in this rare case, researchers in Japan describe a patient ultimately diagnosed with AAV who was referred to a department of rheumatology due to muscle weakness in her lower extremities, which she had been experiencing for the past three months.
One and a half months before the referral, the patient, a 76-year-old woman, could no longer squat or stand by herself and began complaining of dry cough.
She had been diagnosed with interstitial lung disease based on chest radiography results conducted at a neighborhood clinic, but was referred to the rheumatology department for evaluation of her muscle weakness.
Researchers there examined her medical history. They found that she had had Raynaud’s phenomenon — a condition where not enough blood reaches the fingers and toes — for the past 26 years, a history of diabetes and chronic inflammation of the thyroid gland, and otitis, or infection, in both ears four months before referral.
A physical examination showed tenderness in all extremities, and weakness affecting mainly the muscles in the hip region and upper legs.
While a urine analysis didn’t show any problems, blood exams were suggestive of increased inflammation and muscle impairment. Additional testing showed that the patient had several autoantibodies, including anti-ANA, anti-SSA/Ro, and anti-MPO antibodies, and rheumatoid factors, all suggestive of an autoimmune disorder.
Sjögren’s syndrome was ruled out through an eye examination and salivary gland biopsy.
Given her history of dry cough, the patient underwent a computed tomography (CT) scan of her chest, which showed alterations consistent with a diagnosis of nonspecific interstitial pneumonia.
But her muscle manifestations remained unexplained, leading the team to perform a magnetic resonance imaging (MRI) scan of her thighs — which revealed swollen muscles.
A muscle biopsy then revealed small-vessel vasculitis with invasion of white blood cells and atrophy of muscle fibers.
The patient received a final diagnosis of AAV in the muscle with secondary unclassified connective tissue disease, but they say the condition “could be categorized as granulomatosis with polyangiitis, according to the classification for epidemiologic studies.”
The woman started treatment with high-dose prednisolone (1 mg/kg) while she could not walk without an aid, and her muscle weakness improved within a few months.
Half a year later, however, the patient experienced symptomatic relapse with discomfort of her lower extremities. At this point, autoantibodies and inflammatory markers were high but were resolved with a moderate dose of prednisolone plus azathioprine.
She remained in remission for at least one and a half years after the relapse, during which she kept taking 5 mg of prednisolone and 75 mg of azathioprine daily.
“To our knowledge, only three cases of muscle vasculitis due to AAV that presented mainly with muscle symptoms have been reported,” the researchers wrote.
“Interestingly, all the three cases had preceding pulmonary fibrosis, rheumatoid factor, and MPO-ANCA,” and magnetic resonance imaging of the muscles always showed findings consistent with idiopathic inflammatory myopathies, they said.
The team suggests that ab muscle biopsy should be considered in these cases to confirm an AVV diagnosis.