MANNAN-BINDING LECTIN DEFICIENCY IN A CHILD: IS IT A THING OR NOT?

MBL is critical in activating the lectin pathway of the complement system. MBL deficiency remains a contentious issue in clinical practice, mainly because low MBL levels may present in completely asymptomatic individuals. However, in some cases, symptomatic patients may present with susceptibility to infections and even immune dysregulation. Infections may range from mild to severe, and may even be life-threatening and fatal. A significant number of patients may remain undiagnosed, merely because interrogating complement function is often postponed until after presumably more common immune problems have been excluded in patients with severe, recurrent or unusual infections. In addition, clinicians are less familiar with the clinical recognition and appropriate choice of special investigations necessary to diagnose MBL and other complement deficiencies. Our case report describes a young girl with a serious underlying inborn error of immunity. She initially presented with recurrent 'innocent' and mild infections. We illustrate that clinically relevant MBL deficiency, if undiagnosed, may have disastrous consequences. We also stress the importance of careful interpretation of MBL quantitative laboratory values and the urgent need for access to more specialised complement-component and genetic testing, especially for patients attending state healthcare facilities.