Muscle Pain: Is It Polymyositis or Fibromyalgia? - Internal Medicine

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When considering the symptoms you've described, it’s important to differentiate between polymyositis and fibromyalgia, as they present with overlapping but distinct features.
Polymyositis is an inflammatory muscle disease characterized primarily by muscle weakness. Patients often experience difficulty in performing daily activities due to this weakness, which typically affects the proximal muscles, such as those in the hips, thighs, and shoulders. While muscle pain can occur, it is not the primary symptom; rather, the hallmark of polymyositis is muscle weakness that can progress over time. Additionally, patients may have elevated muscle enzymes in their blood tests, such as creatine kinase (CK), which indicate muscle damage.

On the other hand, fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, fatigue, and tenderness in localized areas, often referred to as "tender points." Unlike polymyositis, fibromyalgia does not typically involve muscle weakness or inflammation detectable through blood tests. The pain in fibromyalgia can be described as a deep ache, and patients often report symptoms like sleep disturbances, cognitive difficulties (often referred to as "fibro fog"), and heightened sensitivity to pain.

In your case, the symptoms of widespread muscle soreness, stiffness, and tenderness upon pressure suggest that fibromyalgia may be more likely than polymyositis. The fact that you do not report significant muscle weakness, fever, or other systemic symptoms also leans away from polymyositis. The presence of pain in multiple muscle groups, particularly without a clear cause such as intense exercise or injury, aligns more closely with fibromyalgia.

It's also worth noting that fibromyalgia can be triggered or exacerbated by various factors, including stress, lack of sleep, and physical activity. The discomfort you feel in your legs while sitting and the soreness after running could be indicative of fibromyalgia's characteristic pain patterns.
To further evaluate your condition, it would be beneficial to consult a healthcare professional, preferably a rheumatologist, who specializes in musculoskeletal disorders. They can perform a thorough assessment, which may include a physical examination, blood tests to rule out other conditions, and possibly a review of your medical history and lifestyle factors.
In summary, while both conditions can cause muscle pain, the absence of muscle weakness and the nature of your symptoms suggest that fibromyalgia is a more likely diagnosis. However, a definitive diagnosis can only be made through a comprehensive evaluation by a healthcare provider. If you find that your symptoms are affecting your daily life, seeking medical advice is crucial for appropriate management and treatment options.