If you've been diagnosed with calcific tendinitis, you already know the pattern: calcium crystals form inside a tendon — most commonly the supraspinatus in the shoulder — and cause pain that ranges from a dull background ache to sudden, acute attacks that make simple movements nearly impossible.

Tumoral calcinosis occupies a strange corner of medicine: rare enough that most people wait years for an accurate diagnosis, yet specific enough that once you understand the underlying biology, the clinical picture becomes surprisingly clear.