Polymyositis diagnoses ‘exceedingly rare’ in shift toward inclusion body myositis
Click Here to Manage Email Alerts
SAN DIEGO — Many patients who might have previously been diagnosed with polymyositis are now being treated for inclusion body myositis, according to a speaker at the Congress of Clinical Rheumatology West.
Thomas E. Lloyd, MD, co-director of the Johns Hopkins Myositis Center, suggested that the classification of idiopathic inflammatory myopathies have been “evolving in general” recently.
“Over the last few years, we have seen that polymyositis is exceedingly rare,” he said. “Patients are now more actively diagnosed with inclusion body myositis, or IBM.”
Most patients with this diagnosis are older than 50 years, with the median age being 60 years, according to Lloyd.
“In general, it is a disease of aging,” he added. “We essentially never see it under the age of 30.”
IBM is marked by slowly progressive muscle weakness and wasting. It frequently occurs in the quadriceps and finger flexors, which can cause frequent falls or reduced ability to grip things. The orbicularis oculi may also be impacted, as may the triceps or ankle dorsiflexion. The diagnosis largely occurs in men.
“IBM can be asymmetric, which presents a diagnostic challenge,” Lloyd said.
In fact, diagnostic delays can often stretch as long as 5 years, he added. This delay is at times exacerbated by the older patient population, according to Lloyd.
“Elderly patients are told, ‘You are just getting older, this is just part of aging, you need to exercise more,” he said.
It is often not until a patient’s creatine kinase is checked that they are accurately diagnosed. To make a proper diagnosis, rheumatologists should assess quadricep weakness, along with finger flexor weakness.
“The keys to making a diagnosis of IBM are natural history and physical exam,” Lloyd said. “But the way to make a confirmed diagnosis is with a muscle biopsy.”
According to Lloyd, the selection of which muscle to biopsy is critical. If the biopsied muscle is too weak, the results may suggest just end stage fibrosis.
“We always select muscles that are only mildly weak,” Lloyd said.
Biopsy results may demonstrate auto-invasion of mononuclear cells, rimmed vacuoles or protein aggregates. However, these results may not always be present, so clinicians should also look for mitochondrial abnormalities or immunostaining for MHC-I, TDP-43 or p62 – Anti-NT5C1A (cN1A) antibody.
Most patients will have some type of inflammation, Lloyd noted, adding that approximately half of patients with IBM will develop problems swallowing.
“In most cases, it is mild, but it can lead to a significant source of morbidity and mortality,” he said. Additionally, aspiration pneumonia is not uncommon in the subgroup of patients who have difficulty swallowing.
Turning to management, Lloyd stated physical and occupational therapy are beneficial to patients.
“Exercise is incredibly beneficial,” he said.
According to Lloyd, patients who exercise multiple times a week or twice a day “actually get stronger.”
Training the finger-flexor muscles can also be useful for individuals with that manifestation. Meanwhile, low-impact exercise like water aerobics or walking are generally preferable to more rigorous interventions like weightlifting in this patient population. “Increasing flexibility is critical,” Lloyd said.
Collapse
Lloyd TE. What’s new in inclusion body myositis. Presented at the Congress of Clinical Rheumatology West; Oct. 20-23, 2022 (hybrid meeting).
Read more about
Click Here to Manage Email Alerts