In a suspected case of polymyositis, which finding is most consistent with this diagnosis?

The most consistent finding in a suspected case of polymyositis is weakness of the proximal muscles without pain. Polymyositis is characterized primarily by muscle weakness, especially affecting the proximal muscle groups such as the shoulders and hips. Patients typically present with difficulty in activities like climbing stairs or lifting objects. Notably, this weakness often occurs without associated muscle pain, distinguishing it from other myopathic conditions.

In contrast, the presence of painful proximal muscles without weakness would suggest a different pathology, possibly a muscular strain or a myopathy with pain, rather than polymyositis. A positive Homan's sign is indicative of deep vein thrombosis (DVT), and while this may be a significant concern in a clinical context, it is not associated with polymyositis. Several positive tender points relate more to fibromyalgia or other myofascial pain syndromes rather than polymyositis, which typically does not present with tenderness.

Therefore, the hallmark of polymyositis is indeed the weakness of proximal muscle groups, often found without accompanying pain.