[Hereditary complement C5 deficiency: study of 3 Tunisian adult cases and literature review].

Background: The complement system is one of the main effectors of both innate and adaptive immunity. Hereditary complement deficiency, mainly those of the terminal pathway (C5-C9), is at increased risk for septic meningitides particularly meningococcal ones.

Aim: to assess clinical and biochemical features of 3 Tunisian adults with C5 hereditary complement deficiency (C5D), with a familial study performed for two of them.

Methods: Functional activity of the classical and the alternative pathway of complement (CH50 and AP50 respectively) were measured according to standards haemolytic procedures. Serum concentration of complement components were determined by nephelemetry and ELISA. C5D was diagnosed when CH50, AP50 and C5 antigenic level were highly decreased.

Results: Our patients were 2 men and one woman. All these patients presented clinical symptoms of septic meningitides. Meningococcal orign was confirmed in one case. C5 level varies between 0 and 0.4%. Levels of other complement components: Clq, C3, C4, properdine, C6, C8 and C9 were normal. Antigenic C7 level was 50% in the female patient. Familial study revealed no similar hereditary complement deficiency in relatives.

Conclusion: Only 27 cases with C5D were reported in the literature. The description of 3 cases in our series demonstrates that: * C5D is not rare in Tunisia, ** C5D is clinically commonly complicated by meningitides with unconstant severity, *** C5D is biologically caracterised by a variable level of the plasmatic C5 component.