Definition from Wiktionary, the free dictionary
Humorous formation from dyslexia by metathesis as if due to dyslexia.
- (humorously) Dyslexia.
- (informal) Being prone to metathesis in reading, writing, or speech due to (real or imagined) dyslexia.
- 1990, Sharon Arthur Moore et al., Dyslexia, what's lysdexia? [title] in Reading Teacher 43
- 1995, Jerrold S Maxmen, Essential Psychopathology and Its Treatment 
- More complex problems such as dyslexia (or as one child once said, lysdexia) may merit a variety of special interventions.
- 2003, Willow Polson, The Veil's Edge 
- Priase to Hodwy, Dog of Lysdexia.
- 2005, Stefan Koski, Miscellaneous Philosophy 
- “My apologies. My lysdexia must be kicking in again. What I meant to say was, ‘Who beath thou?’”