CASE PRESENTATION
We report a 38-year-old female patient, previously healthy, presented with high fever, adynamia, diffuse myalgia, and polyarthralgia of hands, wrists, elbows, and knees. She sought medical attention and was diagnosed with CHIKV infection, confirmed by a positive IgM Enzyme-Linked Immunosorbent Assay (ELISA) serological study in two samples. Joint pain and myalgia persisted, and after two months, she presented progressive complaints of fatigue, difficulty combing her hair, walking, and getting out of bed. She had frequent falls, dysphagia for solids, dysphonia, dyspnea on mild exertion, and was bedridden. She was then admitted to the hospital for investigation.
On physical examination, she presented decreased proximal limb muscle strength, grade 2 in lower limbs and grade 3 in upper limbs, according to Medical Research Council (MRC) scale. Pulmonary auscultation presented fine bilateral basilar crackles. Manual muscle test (MMT) of 64 out of 150 points. Locomotor examination showed arthritis in knees and ankles bilaterally.
Complementary examinations revealed elevated creatine phosphokinase (CPK: 25150 U/L [VR: 0 A 170 U/L]) and increased transaminases (TGO: 377 U/L and TGP: 264 U/L [VR: 0 A 31 U/L]). Anti-Jo-1 antibody was reagent (141 U/mL [VR: reagent > 10 U/mL]). Antinuclear antibody (ANA) with a mixed pattern of 1/80 fine dotted nuclear type and 1/160 dotted cytoplasmic type. Electroneuromyography of four limbs confirmed a pattern of myopathy, affecting mostly proximal muscles. Magnetic resonance imaging (MRI) of thighs showed diffuse edema of muscles, without areas of liposubstitution, suggesting an acute inflammatory process (Figures 1 and 2). Chest computed tomography (CT) scan showed ground-glass opacities in bases up to the middle third of lungs, compatible with nonspecific interstitial pneumopathy (NSIP).
The diagnosis of Antisynthetase Syndrome, an immune-mediated inflammatory myopathy, post-Chikungunya infection, was then established. The patient presented with a compatible clinical, with proximal muscle weakness in all four limbs, MRI of thighs showing a muscular inflammatory process, electroneuromyography with a myopathic pattern, interstitial pneumopathy, and a positive Anti-Jo1 antibody, in addition to joint involvement.
Other etiological causes were investigated and ruled out, such as viral infections by hepatitis virus, cytomegalovirus, HIV, syphilis, and COVID-19, metabolic disorders, use of previous medications, and screening for neoplasms, confirming chikungunya as the trigger for myopathy.
Pulse therapy was started with methylprednisolone for 3 days and human immunoglobulin for 6 monthly cycles. The patient had clinical recovery and a gradual decrease in muscle enzymes, reaching 257 U/L (VR: 0 to 170 U/L) after 6 months. She was also given monthly intravenous cyclophosphamide for a period of 6 months due to pulmonary involvement. The patient maintained motor and respiratory physical therapy, evolving with grade V muscle strength in the four limbs, with no complaints of fatigue, dysphagia, or dysphonia.
Figure 1: A) Coronal T1 (hip and thigh images): absence of muscle liposubstitution. B) Coronal T2 with fat saturation (SPAIR technique): Diffuse muscular edema affecting the pelvic girdles and thighs.