Major histocompatibility complex class I deficiency

This code describes a rare primary immunodeficiency disorder characterized by a severe defect in the expression of MHC class I molecules on the surface of cells. This deficiency impairs the immune system's ability to present intracellular antigens to cytotoxic T lymphocytes, leading to recurrent bacterial and viral infections, particularly of the respiratory tract, and neurological abnormalities.

Use this code for patients diagnosed with Major Histocompatibility Complex (MHC) class I deficiency, also known as Bare Lymphocyte Syndrome type I. Documentation should clearly state the diagnosis, often confirmed by laboratory findings showing absent or significantly reduced MHC class I expression on peripheral blood mononuclear cells.

• Ensure documentation specifies "class I" deficiency to differentiate from other Bare Lymphocyte Syndromes.
• Code any associated infections or neurological manifestations separately as secondary diagnoses.
• This is a rare condition; confirm the diagnosis with physician documentation and relevant lab results.