The most common disease of the facial nerve is Bell's Palsy. This disorder affects nerve peripherally. Regarding causation of Bell's Palsy, a viral agent has long been suspected, but its definite cause has not been found yet. Familial occurrence of Bell's Palsy is occasionally seen, so inheritance has been suspected in its ethiology too. In this paper, 6 cases running through two generations of an Iranian family with Bell's Palsy are described. No any other neurologic disorder has been seen among cases. This report demonstrates the role of heredity as an ethiologic factor in Bell's Palsy, and the mode of inheritance possibly to be autosomal dominant inheritance.

Acute idiopathic peripheral facial paralysis (Bell’s Palsy) is the most common disorder of the facial nerve. Most patients recover completely, although some have permanent disfiguring facial weakness. Many studies have attempted to identify an infectious etiology for this disease. Although the cause of Bell’s Palsy remains unknown, recent studies suggest a possible association with Herpes Simplex Virus-1(HSV-1) infection. In this case-control study we investigated the presence of DNA of HSV in the saliva of 26 patients with Bells Palsy in first and second weeks of disorder compared to normal population who were matched in sex, age, as well as history of diabetes mellitus, hypertension and labial herpes. In the case group 3 and 7 patients had positive polymerase chain reaction (PCR) for HSV in first and second weeks of disease respectively compared to 4 in controls. It means that there was not any relationship between Bell’s Palsy and HSV in saliva either in first or in second week. Two and 6 of positive results from the sample of first and second weeks were from patients with severe (grade 4-6) Bell's Palsy. Although the positive results were more in second week in patient group and more in severe palsies, but a significant relationship between Bell's Palsy or its severity and positive PCR for HSV was not detected (P >0.05).