Search

Myalgia is a classical sign in invasive meningococcal diseases (IMD), but severe and persistent myalgia following an IMD have never been reported to date.A 20-year-old man presented with purpura fulminans and meningitis caused by Neisseria meningitidis serogroup Y, revealing properdin deficiency. Although meningitis symptoms improved after antibiotherapy, initial myalgia of the lower limbs increased, associated with mild rhabdomyolysis. Magnetic resonance imaging (MRI) revealed an increased STIR (Short TI inversion recovery) signal of both quadriceps muscles, without abscess. After exclusion of other causes of myopathy, a post-infectious myositis was diagnosed. A four-week course of corticosteroids led to dramatic improvement.Post-infectious inflammatory myopathy should be suspected in case of severe and persistent myalgia associated with rhabdomyolysis following an IMD, after exclusion of pyomyositis especially. A short course of corticosteroids seems to be effective.

Sixty one Tunisian adult patients with bacterial meningitis were screened for complement deficiency. Functional activity of the classical and the alternative pathways of complement (CH50 and AP50 respectively) were measured according to standard haemolytic procedures. Serum concentrations of C3 and C4 were determined by nephelometry. Late complement component (C5-C9) and properdin concentrations were assessed by double-ligand EISA. Complement deficiency was found in eight patients (13%): Seven had late complement component deficiency (three C7 deficiency, two C5 deficiency, one C6 deficiency and one C8 deficiency) and one had partial properdin deficiency. Patients with late complement component deficiency had a mean age of 24 years (range 17-32 years). All deficient patients had meningococcal meningitis. Recurrent meningitis was reported in half of the patients. Our findings demonstrated a high prevalence of complement deficiency in Tunisia suggesting that screening for hereditary complement deficiency should be performed in case of bacterial meningitides and meningococcal disease patients.

The complement system plays an important role in defence of the host against infection and in the clearance of immune complexes. Defects in complement proteins are often associated with infections or auto/immune complex diseases. Investigation of complement is useful for diagnosis and following of auto-immune diseases. The aim of this Article is to provide an overview of important applications of complement in medicine, emphasizing the role of complement in pathogenesis and the usefulness of measurements of complement proteins in diagnosis and assessment of the evolution of disease states. Emphasis has been placed on practical applications and understanding basic mechanisms of disease. The best screen for complement deficiencies or significant activation is the CH50, which measures total classical pathway activity and the measurement of C3 and C4. The absence or decrease of multiple components is usually due to consumption of complement. Complete lack of CH50 associated with normal C3 antigen is a strong indication for complement deficiency and should be followed up with further tests to determine which component is missing.

Properdin is one of the regulatory proteins of the alternative pathway of the complement system. Human properdin deficiency is an X-linked disorder strongly predisposing to meningococcal disease. Total deficiency (type I), partial deficiency (type II), and deficiency due to a dysfunctional molecule (type III) can be differentiated immunochemically. Four males in a family showed a selective partial deficiency of properdin. These individuals had 10% of normal properdin concentration in plasma, as measured by ELISA, while the other complement components were normal. Two of the properdin-deficient individuals in two generations had meningococcal infections. Two were clinically healthy at the time of investigation. Measurement of plasma levels of properdin has to be performed in the case of Neisseria meningitidis, especially where there is a previous history of severe bacterial infections in the same family as measurement of CH50 activity is ineffective for screening properdin deficiency.

The dual role of the alternative complement pathway in recognition of foreign substances by a non-immune host and in the intrinsic regulation of the complement sequence is now well recognized. Activation of this pathway occurs through escape from its regulatory mechanisms induced by the activating principle; its functional expression depends on the respective levels of the component proteins C3, factor B, factor D and properdin, and on the control proteins beta 1H and C3bINA. This article presents recently acquired knowlege on the molecular mechanisms of activation, regulation and behaviour under pathological conditions of the alternative complement pathway.

The alternative complement pathway comprises three component proteins C3, B, D and three regulatory proteins P, H and I. These plasma proteins represent the major humoral defense mechanism against infection in a non-immune host. The following topics are reviewed: biochemistry of the alternative pathway proteins; molecular mechanisms of activation and regulation of the pathway; involvement of the alternative pathway in human diseases.

In vitro, the drug pentosan-poly-sulfoester (PPS) changes the electrophoretic migration of different proteins from the complement and properdin systems, such as native C3 (beta 1C globulin), C3c (beta-1A globulin), C3d (alpha-2D globulin), C1s inactivator (ClsINA), Clq and properdin factor B (B). Their more anodal migration is the consequence of a molecular alteration and persists after prolonged dialysis. These structural changes, yet undefined, explain the loss of functional activity of these proteins, and the anticomplementary activity of this drug. Moreover, PPS is able to block the alternate pathway activation by its action on properdin factor B (C3 proactivator). In fact, in presence of PPS, the activators of the properdin systems such as C3 nephritic factor are inactive. These altered mobilities are also responsible for the overestimation in the antigenic concentration of B (+ 45%), C4 (+27%) and C3/C3c (+ 14%), found in human serum containing 50 mg/ml of PPS. PPS has an original action upon the complement and properdin systems, which allows its clinical use as a potent inhibitor of the humoral mediators of inflammation.

The alternative complement pathway comprises three component proteins C3, B, D and three regulatory proteins P, H and I. These plasma proteins represent the major humoral defense mechanism against infection in a non-immune host. The following topics are reviewed: biochemistry of the alternative pathway proteins; molecular mechanisms of activation and regulation of the pathway; involvement of the alternative pathway in human diseases.