In primary care, musculoskeletal complaints are among the most frequent reasons for consultation. While most cases reflect benign mechanical pathology, a small part may represent early manifestations of systemic autoimmune disease. Recognising warnings signs, patients health education and ensuring timely reassessment are essential roles of the family doctor.A 63-year-old man attended an urgent consultation at a Primary Health Care Center with a 2-week history of low back and right hip pain radiating to the thigh after exertion. Examination suggested a mechanical cause and symptomatic treatment was provided. As part of standard care, the patient was informed of the warning signs that should prompt urgent reassessment. Three days later, the patient presented to the emergency department with persistent myalgias, cervical pain, and fever. Laboratory tests revealed marked inflammatory responses, with widespread pain disproportionate to physical findings. Extensive imaging and infectious analyses showed no source. During hospitalisation, inflammatory markers rose despite empirical antibiotics. MRI of the lower limbs showed multifocal edema and autoimmune analysis revealed a strongly positive anti-Jo-1 antibody, leading to the diagnosis of antisynthetase syndrome. Corticosteroid therapy produced a rapid improvement. The patient was discharged for follow-up with Internal Medicine and Primary Health Care physicians.Anti-synthetase syndrome is rarely first detected in primary care. Published reports describe presentations with interstitial lung disease or myositis. In contrast, this case initially mimicked common mechanical pain without respiratory involvement or elevation of muscle enzymes, which is unusual. This highlights the diagnostic challenge for physicians.Persistent or atypical musculoskeletal pain, especially with systemic symptoms, should prompt diagnostic reconsideration. Providing follow-up safety advice remains essential, as demonstrated here with clear communication of alarm signs that allowed effective patient guidance. Long-term primary-care follow-up is crucial for monitoring immunosuppression, infection prevention, comorbidity management, and patient education.Early recognition of red flags, appropriate escalation of care and multidisciplinary collaboration are key to improving outcomes in rare conditions that first present as seemingly routine primary-care problems.This case illustrates the difficulty of identifying rare autoimmune myopathies in a clinical context largely characterized by benign musculoskeletal complaints highlighting the importance of the continuity of care and the multidisciplinary collaboration.