According to http://pumka.net/2009/12/19/reading-writing-and-converting-rsa-keys-in-pem-der-publickeyblob-and-privatekeyblob-formats/ MSPRIVATEKEYBLOB and MSPUBLICKEYBLOB are acceptable parameters for -outform / -inform for rsa.
The official OpenSSL docs, however, make no mention of these parameters:
https://www.openssl.org/docs/man1.0.1/apps/rsa.html
This kinda makes me wonder.. what other undocumented parameters can -outform and -inform?