Coexistence of multiple myeloma with inammatorymyopathy: an incidental nding of increased generalised  proximal muscles metabolic activity in a patient of theknown case of multiple myeloma

Background

Inammatory myopathy is a spectrum of systemic conditions that presents as progressivemuscle weakness caused by inammation in muscles.In certain conditions it could be presented as extramuscular involvement such as parane-oplastic conditions.As a plasma cell neoplasm, multiple myeloma is often presented with multiple bone painbut association with myalgia is often rare in consideration of the same.As reported in the case report by Valeria Guglielmi at el in 2017and 2020, that borte-zomib induced muscle toxicities in patients that received VRD regimen chemotherapy (VRD(Velcade (bortezomib) + Revlimid (lenalidomide) + dexamethasone)) manifested as proximalmuscle weakness in (07 out of 24 patients) in spite of being muscular markers were normal.They also concluded the mechanism of muscle injury associated with bortezomib remains tobe elucidated. In patients a metabolic myopathy consisting of lipid accumulation within mus-cle bers was documented. The presence of mitochondrial abnormalities at ultrastructurallevel suggests that lipid deposits in muscle can be secondary to mitochondrial dysfunction;

 In the absence of abnormalities in the organic acid and acylcarnitine proles as well as in thefree and total carnitine levels rules out other causes of lipid storage myopathy.Theyfurtherillustratedthedirecteectofbortezomibonprimaryhumanmyoblasts. Theirstudydemonstratedthathumanmusclecellsexhibitedadose-andtime-dependentdecreaseincell viability only in response to relative high concentrations of bortezomib (10 and 20 nM).Bortezomibusedat5nM,whichistherangeofplasmaconcentrationfollowingadministrationof 1.3 mg/m2 in patients.As it is also known that at high concentration bortezomib can alter the catabolic processof autophagy in primary human myoblasts.

The case

A 51 years old lady, known case of multiple myeloma. presented to the department of nuclearmedicine, JIPMER on 15.10.2020 with history of multiple joints and bone pain for the past8 months as of (27.02.2020). Initially evaluated elsewhere at a local hospital where She wasevaluated with an X-ray skull on (18/2/20) that showed lytic lesions. Plasma electrophoresis(20/02/20) M-Band (7.5 g%). Albumin to globulin ratio was 0.54. On course of treatmentIFE done on 23/02/2020 suggestive of IgG kappa monoclonal gammopathy. Bence Jonesproteinuria is present in urine. Bone marrow biopsy (26/02/20) multiple myeloma. Then thepatient was referred to the department of medical oncology, JIPMER Puducherry; where shewas started on Chemotherapy with VRD (Velcade (bortezomib) + Revlimid (lenalidomide) +dexamethasone)6cyclescompleted(lastdoseon01/10/2020). Bonemarrowbiopsy(6/10/20)morphologically in remission.In October 2020, for one week she complained of progressive myalgia of bilateral upperand lower limbs. On request to assess the treatment response work up, F18 FDG PET CT wasdone on 15.10.2020.

F-18 FDG PET/CT on 15.10.2020:

The patient was instructed to have a minimum of 6 hours fasting before thescan procedure. On arrival of the patient, clinical history was noted fol-lowed by the oral consent taken while describing the procedure. Procedure:F18 FDG was administered intravenously followed by the acquisition of thewhole-body PET/NCCT images vertex of skull to toe after 70 minutes.Measured activity: 5.4 mCi at 09:56 AM; Administered time: 09:58 AM;Post injection: 0.08 mCi. Fasting blood glucose was 122 mg/dl.

 Scan interpretation and nding:

1. semiquantitative evaluation: on visual interpretation of maximum intensity projection(MIP) images, a region of interest has been drawn over the liver and mediastinal bloodpool then after the region of interest was drawn in the group of muscles showing themaximum semi-quantitative uptake value (SUVmax); lastly, the ratio of former withlater one is compared.Table: The proposed semiquantitative scoreIn fused images Generalised diuse muscle uptake of F-18 FDG was noted in exor com-partment muscles of the bilateral lower limbs which was markedly increased n comparison toliver/mediastinal blood pool background.1. On visual interpretation, there were features suggestive of generalised proximal musclemyopathy.

 

 Dubey, G.K. (2021). Coexistence of multiple myeloma with inammatory myopathy: an incidentalnding of increased generalised proximal muscles metabolic activity in a patient of the known case of multiplemyeloma.

Conclusion

There are very few case reports available showing the same kind of drug-induced myopathyin patients receiving VRD regimen caused the depletion of myoblasts causing inammation.