Familial Mediteranean Fever is a disease that is transmitted in an autosomal
recessive fashion. It consists of bouts of fever, joint pain and abdominal
and sometimes chest pain. The bouts are generally self limited but painful.
Cholchicine has been shown to diminish the frequency of attacks. The reason
you see little of it in the literature is that it is rather infrequent in
the US (It is barely mentioned in Nelson Textbook of Pediatrics. Rudolph's
textbook has more information.) It is rather common here in Israel as it is
most likely in those of Mediterranean extraction such as North Africa. Plain
and simple, the AAP considers it compatible with breastfeeding thus I see no
reason why your client should be concerned.  It is used in young children
with FMF also. According to the references in Briggs, Friedman and Yaffee
there seems to more concern about using it in pregnancy that in lactation.