The word undiagnosed is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 18
Highest Scoring Words With Friends™ Plays In The Letters undiagnosed
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Seven Letter Word Alert: (27 words)
adenoid, adonise, agonies, agonise, anodise, dandies, dousing, dungeon, endings, ensuing, gaudies, godsend, guanine, guineas, igneous, inuendo, nodding, sanding, sending, snudged, sodding, sounded, unaided, undined, undines, undoing, undosed