Can pemphigus be hereditary?

Not really. Pv, pemphigus vulgaris, is not thought to be a genetic disease. However, a family history of pv might increase your risk. As of yet, no pv gene has been found that when mutated conveys the disease.
No. Medical genetics has not found a pemphigus gene & pemphigus does not appear to run in families. Like many diseases there are certain transplantation genes associated with pemphigus. If you have one or more of these genes you are at a slightly increased risk for developing pemphigus. The emphasis here is on slightly.