Mode of inheritance in systemic lupus erythematosus in Saudi multiplex families.

Systemic lupus erythematosus (SLE) is a an autoimmune disease causing inflammation and injury of multiple organs like joints, skin, kidneys, eyes, central nervous system, heart. The etiology of SLE remains unknown. However; genetic component significantly contributes to the etiology of SLE. Familial SLE patients were defined as a family with more than one sibling diagnosed with SLE. The objective of the study is to describe the clinical features of the familial SLE and analyze the family pedigrees. Twenty-five individuals with SLE belonging to seven Saudi families were included. Three-generation pedigree was taken from the candidate families. The mean age at onset of the disease was 84.5 months (range: 18-144) while the mean age at diagnosis was 90.6 months (range: 24-144) and the mean duration of follow up was 48.5 months (range: 7-108). The proportion of girls was predominant (78%). Malar rash, arthritis and nephritis were the more frequent features. Sixteen patients had renal lesions, 10 of them had class VI nephritis according WHO classification. Five of the seven families are consanguineous reflecting the high percentage of consanguinity in our population. As many other autoimmune diseases, multifactorial is the most common form of inheritance. In the current study, the suggested mode of inheritance is autosomal recessive assuming Mendelian inheritance of single gene disorder.