Most spell checkers have to be trained extensively to understand technical vocabulary used in academia, engineering and medicine. Wiktionary and Wikipedia however have great collections of these words and their definitions neatly packed in categories.
This cli application downloads and extracts vocabulary from Wiktionary pages and stores them as .dict files for your spell checker.
gutenspell -o medical https://de.wiktionary.org/wiki/Verzeichnis:Deutsch/Medizin