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PubMed This is a summary of 4 peer-reviewed journal articles Updated
Clinical Immunology · Bare Lymphocyte Syndrome Type I

Signs, Symptoms, and the Risks of Misdiagnosis

At a Glance

Bare lymphocyte syndrome type I can cause recurrent lung infections, bronchiectasis, slow-healing skin sores, and uveitis. Because these problems may resemble autoimmune disease, infections should be assessed before or alongside medicines that suppress the immune system.

Bare Lymphocyte Syndrome Type I (BLS-I) presents a unique set of challenges because its symptoms can mimic more common conditions. While some individuals remain healthy for years, many experience reported patterns of symptoms: chronic lung issues, persistent skin sores, and eye inflammation [1]. Understanding these signs is crucial for getting the right care and avoiding dangerous treatment mistakes.

The Respiratory Cycle: Infections and Bronchiectasis

For many with BLS-I, the first signs of the condition involve the respiratory system. Because the immune system cannot properly “see” and eliminate certain threats, common germs can cause lasting damage [1].

  • Recurrent Sinopulmonary Infections: This refers to frequent, repeated infections of the sinuses and the lungs [2]. While many people get occasional colds, those with BLS-I may find that their infections are more frequent, more severe, or take longer to clear.
  • Bronchiectasis: Over time, repeated lung infections can lead to bronchiectasis. This is a condition where the airways in the lungs become permanently widened, thickened, and scarred [1]. This scarring makes it even harder to clear mucus, which can lead to more infections—creating a difficult cycle. In one small study, 10 out of 11 patients with BLS-I had developed bronchiectasis [1].

Skin and Eye Manifestations

BLS-I often affects parts of the body outside the lungs. Two of the most common areas are the skin and the eyes.

  • Granulomatous Skin Lesions: These are deep, chronic skin ulcers or sores that may look like they are “eating away” at the tissue (necrotizing) [2]. They often appear on the legs or the face and can be very slow to heal [1]. Interestingly, researchers have found that vaccine-strain rubella virus may sometimes be detected inside these sores in some TAP-deficient patients, driving the inflammation [2].
  • Uveitis: This is inflammation of the middle layer of the eye (uvea) [1]. It can cause pain, redness, or blurry vision and can lead to permanent eye damage if not managed. About half of the patients in one clinical group experienced uveitis [1].

The Challenge of Misdiagnosis

One of the most critical risks for someone with BLS-I is being misdiagnosed with an autoimmune disease. Because the skin sores and lung issues look like they are caused by an overactive immune system, doctors may mistake BLS-I for conditions like granulomatosis with polyangiitis (a type of vasculitis) [3][2].

If a doctor prescribes systemic immunosuppressants (drugs like high-dose steroids or chemotherapy-like medications that weaken the entire immune system) to treat what they think is an autoimmune issue, it can have severe consequences [3]. Since the patient already has a weakened immune system, these drugs can lead to life-threatening infections and increased morbidity (illness) [2][3].

However, you should never start or stop prescribed medications without the treating team. Immunosuppression is sometimes necessary for uveitis or other inflammatory complications. The key is to evaluate lesions for infection before or alongside immunosuppressive therapy, coordinating your immunology, dermatology, and infectious-disease care.

Urgent Warning Signs

While many infections in BLS-I can be managed, certain symptoms require immediate medical attention. Be alert for:

  1. Bronchiectasis Emergencies: Seek immediate care for severe or rapidly worsening breathlessness, coughing up blood, low oxygen readings, chest pain, confusion, or persistent high fever with rapid deterioration.
  2. Unexpected or Severe Viral Infections: Infections from the herpes family, such as herpes zoster (shingles), can be particularly severe in some people with BLS-I [4][3].
  3. Symptoms After Starting New Meds: If you are started on an immunosuppressant and develop a new fever, a sudden change in your cough, or a rapidly spreading skin redness, contact your care team immediately [2][3].
  4. Sudden Vision Changes: Any new eye pain or sudden blurring could indicate a flare of uveitis that needs urgent evaluation by an ophthalmologist [1].

Managing BLS-I is about finding a balance—treating the symptoms while protecting the immune system you have. Always advocate for an “infection-first” approach when a new symptom appears.

Common questions in this guide

What symptoms can bare lymphocyte syndrome type I cause?
BLS-I can cause repeated sinus and lung infections, and those infections may lead to bronchiectasis, permanent widening and scarring of the airways. It can also cause deep, slow-healing skin sores and uveitis, an inflammation inside the eye.
Why is BLS-I sometimes mistaken for an autoimmune disease?
Chronic skin lesions and lung problems can look like inflammation from autoimmune vasculitis, including granulomatosis with polyangiitis. The distinction matters because medicines that broadly suppress the immune system can increase the risk of severe infections in someone with BLS-I.
Should a BLS-I skin sore be checked for infection before immunosuppressants?
A skin sore should generally be evaluated for infection before or alongside consideration of immunosuppressive treatment. The treating team can use the lesion's appearance, test results, eye or other inflammation, and the person's overall condition to guide the decision.
When does someone with BLS-I need urgent medical attention?
Get urgent care for severe or rapidly worsening shortness of breath, coughing blood, low oxygen, chest pain, confusion, or a high fever with rapid deterioration. New severe viral symptoms or sudden eye pain or blurred vision also need prompt assessment.
Can BLS-I lead to bronchiectasis?
Yes. Repeated sinus and lung infections can damage the airways, causing them to become permanently widened, thickened, and scarred; this is called bronchiectasis. Bronchiectasis can make mucus harder to clear and may contribute to more infections.
What should I do if my fever or cough changes after starting an immunosuppressant?
Contact your treating team immediately if you develop a new fever, a sudden change in cough, or rapidly spreading skin redness after starting an immunosuppressant. Do not start or stop prescribed medicines on your own; your team can decide whether infection testing or urgent treatment is needed.
Why might someone with BLS-I need an eye examination?
BLS-I can be associated with uveitis, inflammation of the middle layer of the eye. It may cause pain, redness, light sensitivity, or blurred vision and can damage sight if untreated, so discuss an ophthalmology evaluation with your care team, especially if eye symptoms appear.

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References

References (4)
  1. 1

    Clinical and immunological spectrum of MHC class I deficiency: insights from a long-term cohort with two novel mutations.

    Haskologlu S, Ikinciogullari A, Islamoglu C, et al.

    Frontiers in immunology 2025; (16()):1675097 doi:10.3389/fimmu.2025.1675097.

    PMID: 41126834
  2. 2

    TAP-I Deficiency Presenting With Chronic Granulomatous Rubella Virus-Driven Cutaneous Ulceration: A Case Report and Scoping Literature Review.

    Ponsford MJ, Carne EM, Bramhall K, et al.

    Journal of clinical immunology 2025; (46(1)):1 doi:10.1007/s10875-025-01919-6.

    PMID: 41298860
  3. 3

    Inborn errors of immunity affecting the MHC class I pathway for antigen presentation.

    Gadola SD, Ardeniz Ö, Cuapio A, et al.

    Journal of human immunity 2025; (1(2)):e20250029 doi:10.70962/jhi.20250029.

    PMID: 42169988
  4. 4

    Phenotypic and pathomechanistic overlap between tapasin and TAP deficiencies.

    Elsayed A, von Hardenberg S, Atschekzei F, et al.

    The Journal of allergy and clinical immunology 2024; (154(4)):1069-1075 doi:10.1016/j.jaci.2024.06.003.

    PMID: 38866210

This page is for informational purposes only and does not constitute medical advice. Do not start or stop immunosuppressants or antibiotics without your treating team's guidance; seek urgent care for severe breathing problems or sudden vision changes.

Guide contents Immunodeficiency by defective expression of MHC class I
Research & Literature
01 Understanding Bare Lymphocyte Syndrome Type I (BLS-I) 03 The Biology of BLS-I and How It Is Diagnosed