Does craniosynostosis and palmar crease occurring together indicate a genetic abnormality or another condition all together?

Not specificly: Craniosynostosis(cs) does occur with named syndromes & some have a single palm crease. However, those entities have other dramatic features that aid their diagnosis. Cs most often occurs in isolation @ .4-1/1000 births with a variety of gene influences giving recurrence risk ~1-2%. A single palm crease occurs in 4% of newborns.Consultation with a medical geneticist may clarify your situation.

Craniosynostosis: An interesting question and I would suggest that you see a pediatric genetist that deals with craniofacial disorders as they can work this up further and see if there is a relationship.