Also known as MHC class II deficiency or bare lymphocyte syndrome type II (BLS-II), is a rare genetic disorder that affects the immune system's ability to recognize and respond to foreign substances, such as bacteria, viruses, and other pathogens. This condition is characterized by a deficiency of major histocompatibility complex class II (MHC class II) molecules on the surface of immune cells called lymphocytes.


  • Can be caused by mutations in various genes that are involved in the production and regulation of MHC class II molecules. There are different types of BLS, each associated with specific genetic mutations. The severity of the disorder can vary depending on the specific gene mutations and their impact on MHC class II expression and function.
  • Individuals with BLS are more susceptible to recurrent infections, particularly bacterial, fungal, and viral infections. These infections can be severe and may affect various organ systems. Early diagnosis and treatment are important to manage and prevent complications associated with these recurrent infections.


  • Recurrent Infections: Individuals with BLS are prone to frequent and severe infections, including bacterial, viral, and fungal infections. These infections can affect various organ systems and may include respiratory, skin, and gastrointestinal infections.
  • Respiratory Infections: Recurrent respiratory infections, such as pneumonia, bronchitis, and sinusitis, are common in individuals with BLS. These infections can be severe and difficult to treat.
  • Skin Infections: Skin infections, including cellulitis and abscesses, may occur due to the compromised immune response in individuals with BLS.
  • Gastrointestinal Infections: Gastrointestinal infections, such as gastroenteritis, may lead to symptoms like diarrhea, vomiting, and abdominal pain.
  • Delayed Growth and Development: Some individuals with BLS might experience delayed growth and development due to the chronic nature of infections and their impact on overall health.
  • Autoimmune Disorders: In some cases, individuals with BLS may be at an increased risk of developing autoimmune disorders, where the immune system attacks the body's own tissues. This can lead to a range of symptoms depending on the specific autoimmune condition.
  • Failure to Thrive: Infants and young children with BLS might experience failure to thrive, characterized by inadequate weight gain and growth due to frequent infections and poor overall health.
  • Increased Susceptibility to Opportunistic Infections: Opportunistic infections, caused by typically harmless microorganisms that take advantage of a weakened immune system, can be a significant concern in individuals with BLS.
  • Chronic Diarrhea: Chronic diarrhea may occur in some individuals with BLS due to gastrointestinal infections and impaired immune response.
  • Lymphopenia: A decrease in the number of lymphocytes (a type of white blood cell) may be observed in individuals with BLS, as MHC class II molecules play a role in lymphocyte development and function.


  • Clinical Evaluation: A thorough medical history and physical examination are conducted to assess the patient's symptoms, medical history, family history of immunodeficiencies, and any recurrent or severe infections. Clinical signs may include recurrent respiratory, skin, and gastrointestinal infections.
  • Laboratory Tests: Various laboratory tests are performed to evaluate the patient's immune system function and detect potential abnormalities:
  • Complete Blood Count (CBC): This test can reveal abnormalities in the numbers and types of blood cells, including lymphocytes.
  • Immunoglobulin Levels: Measurements of immunoglobulins (IgG, IgA, IgM) are taken to assess the patient's antibody levels, which can provide insights into immune system function.
  • Lymphocyte Subset Analysis: Flow cytometry is used to determine the numbers and percentages of different types of lymphocytes, including T cells, B cells, and natural killer (NK) cells.
  • Functional Assays: Functional tests may be performed to assess the ability of immune cells to respond to specific stimuli, such as antigens or mitogens.
  • MHC Class II Expression: Definitive diagnosis of BLS involves the assessment of MHC class II molecule expression on the patient's immune cells. This is typically done using flow cytometry or other specialized techniques. A lack of MHC class II expression on immune cells confirms the diagnosis of BLS.
  • Genetic Testing: Once MHC class II deficiency is suspected, genetic testing is often conducted to identify the specific gene mutations responsible for the disorder. Genetic analysis can provide insight into the underlying genetic defects that lead to the deficiency of MHC class II molecules. Genetic testing can help differentiate between different types of BLS and guide treatment decisions.


  1. Aconitum napellus (Aconite): Often used at the onset of colds, flu, or sudden illnesses. It's believed to help boost the body's natural defense mechanisms.
  2. Arsenicum album: Sometimes used for individuals with weakened immune systems who are prone to frequent infections.
  3. Thuja occidentalis (Thuja): Occasionally recommended for conditions related to skin and immunity.
  4. Silicea: Believed by some homeopaths to support the body's ability to fight infections and promote overall health.
  5. Echinacea: Though more commonly known as an herbal remedy, Echinacea is also used in homeopathy for immune support.
  6. Sulphur: Sometimes considered for individuals with chronic skin issues or other chronic conditions believed to be linked to immune dysfunction.