CASE REPORT
An 81 years old male with the history of dilated cardiomyopathy and
congestive heart failure and an operated gastrointestinal stromal tumor
(GIST) of stomach 8 years ago was admitted due to urinary tract
infection. He had progressive loss of weight of approximately 50 pounds
and muscle strength in the last 6 months and was completely immobile for
the last four months. On physical examination, he was left-handed, grip
impairment and diffuse loss of muscle strength on extremities
prominently at distal of right upper limb and proximal of lower limbs as
3/5 without any rash, arthritis, and organomegaly were seen. Owing his
comorbidities, he was under dabigatran, furosemide, bisoprolol, and 400
mg/day of imatinib for the last 8 years. The patient declared that he
gave up routine oncologist follow-up for 5 years and continued to take
imatinib only. Laboratory showed hemoglobin 9.9 gr/dl, white blood cells
11800 109cell/L, neutrophils 9900
109cell/L, CRP 167 mg/L, creatinine 1.4 mg/dL, albumin
2.9 gr/dL, and pyuria on urine analysis. Liver enzymes, thyroid function
tests, and coagulation parameters were normal. After antibiotherapy,
acute phase reactants returned to normal range.
Owing to systemic symptoms and progressive muscle weakness; serologic
tests including anti-nuclear antibody (ANA), extractable nuclear antigen
(ENA) panel, anti-jo1 antibody, and serum creatine kinase (CK) levels
were requested and found in normal range. In bilateral thigh MRI both
acute and chronic findngs of muscle damage were observed. Figure 1 a and
b shows signal changes consistent with focal myositis were observed in
the bilateral quadriceps femoris muscles, especially in vastus medialis
muscles with right side dominance, and atrophic fatty degeneration in
the distal musculotendinous junction of the semimembranosus muscle most
prominently. Both muscle atrophy and asymmetric fatty infiltrations
suggesting chronic changes, and hyperintensity on T2-weighted
fat-suppressed images suggesting acute myositis with normal levels of CK
were consistent with IBM.
Electromyography revealed sural and supperoneal sensory
unresponsiveness, prolongation in the distal latency of the median
response on the right in sensory, while long distal latency and low
amplitude of the median, ulnar and tibial responses, and peroneal
unresponsiveness on the right were observed in motor nerve conduction
studies. In the needle EMG examination, short-term, polyphasic,
low-amplitude motor unit action potentials (MUAPs) and early
participation patterns were observed in right deltoid, biceps, first
distal interosseus, vastus medialis, and iliopsoas muscles and bilateral
tibialis anterior and gastrocnemius muscles. All were interpreted as
diffuse myogenic involvement in both neurogenic and myopathic manner.
PET/CT was performed to evaluate any recurrence or metastasis of GIST
and exclude paraneoplastic causes and revealed physiological FDG uptake
except for chronic inflammation due to remitting epididymoorchitis in
the right testis. Urological evaluation, upper gastrointestinal
gastroscopy, and colonoscopy were benign with no findings of relapsed
GIST.
Biopsy taken from the right quadriceps femoris muscle revealed type 2
atrophy with fatty replacement, diffuse degeneration-regeneration,
red-rimmed vacuoles, ragged red fibers indicating mitochondrial
abnormality, and focal MHC-I positivity on muscle tissue with
inflammatory cell infiltration but not vasculitis and found to be
compatible with IBM (Figure 2 a, b, c, and d).
Imatinib was discontinued because there was no indication of use with
proven disease remission and no other suspicious reason or malignancy
was detected for IBM development. The absence of dysphagia and resistive
infection led us to follow-up him without IvIg administration. One month
after imatinib cessation, he was able to sit in bed and his weight was
stable. In the fourth month, his weight gain was evident, and both
general health status and muscle weakness were improved. At his last
examination, grip impairment was resolved and MRC grades of both upper
and lower limbs were 4-5/5. He became more independent and mobile in
bed, started to eat own his own. Since no benefit was expected from
immunosuppressive therapy; nutritional support, physical therapy and
rehabilitation were given with periodic dysphagia evaluation and
concurrent neurology follow-up.