OBSOLETE: X-linked mendelian susceptibility to mycobacterial diseases due to CYBB deficiency

X-linked Mendelian Susceptibility to Mycobacterial Diseases due to CYBB deficiency (also called X-linked MSMD due to CYBB deficiency) is a very rare inherited immune disorder that makes affected individuals highly vulnerable to infections caused by mycobacteria. Mycobacteria are a group of germs that include the bacteria causing tuberculosis (TB) and a related group called nontuberculous mycobacteria (NTM), as well as the BCG vaccine strain. In this condition, a specific gene called CYBB, which normally helps certain immune cells (called macrophages) produce reactive oxygen molecules to kill germs, does not work properly. Unlike classic chronic granulomatous disease (CGD), which also involves the CYBB gene, this particular form of the disease mainly affects the ability to fight mycobacteria rather than causing the broad range of infections seen in CGD. This is because the CYBB defect in this condition specifically impairs a respiratory burst pathway within macrophages but may leave other immune cell functions relatively intact. Affected boys typically develop severe or recurrent infections after exposure to BCG vaccination or environmental mycobacteria, often in early childhood. Symptoms can include persistent fevers, swollen lymph nodes, lung infections, and widespread (disseminated) mycobacterial disease that does not respond well to standard treatments. Treatment involves long-term antimycobacterial antibiotics and sometimes the use of interferon-gamma therapy to boost the immune response. In severe cases, bone marrow transplantation (hematopoietic stem cell transplant) may be considered. Note that this Orphanet entry is marked as 'OBSOLETE,' meaning it may have been reclassified or merged into a broader category of Mendelian susceptibility to mycobacterial diseases.

Bring these to your next appointment

• Q1.What specific CYBB mutation does my child have, and how does it affect immune function?,Should my child be on long-term preventive antibiotics, and what are the side effects?,Is interferon-gamma therapy recommended for my child, and how is it given?,Is bone marrow transplant an option, and what are the risks and benefits?,What infections should I watch for, and when should I go to the emergency room?,Should other family members be tested for this condition or carrier status?,Are there any vaccines my child should avoid besides BCG?

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