I had a quick look through a DYM family on Geni and noticed that one of these is married to a member of the TOLEDANO family - a well known Moroccan Rabbinic family. So maybe your husband has also this family in his blood.
These are probably living people so the profiles are kept private there, but try and contact the profile mangers on the following profile:-
Also, I found the kohanic family on Geni, so you might want to ask if the profile manager on the above link knows if/how his family is connected to the big family.
I also found the following:-
Look at page 67:-
<<<Molecular genetics and epidemiology: DYM gene (chromosomal locus 18q12-q21.1) In a Moroccan Jewish family six out of 10 sibling were affected. No molecular studies have been reported.>>>
The name of the gene might be that because it was discovered by O. Dym - see page 82, thus no relevance to the family, but the people who asked your husband might have had this information and wanted to find out whether there was a connection.
Ma'aleh Adumim, Israel
Researching: ZIANTS, ZENETSKY (SCHLOSBERG), ZIANTSCHIK, FRIEDMAN, ISMACH (DAVIDSON, OSMAN) from Narewka, Bialystok, Lomza, Lodz, Bielsk, Warsaw; GEWELBA (GABLE,RAVELLE,GALE), SINGER from Warsaw; REINA from Netherlands; MICHAELS from UK & Western Europe; VIEYRA, JUDA-RODRIGUEZ from UK, Netherlands (as well as all other Dutch Sephardi families).