U.S. flag

An official website of the United States government


Send to:

Choose Destination

MHC class I deficiency

MedGen UID:
Concept ID:
Disease or Syndrome
Synonyms: Bare lymphocyte syndrome type 1; BARE LYMPHOCYTE SYNDROME, TYPE I; BLS, TYPE I; HLA CLASS I DEFICIENCY
SNOMED CT: Immunodeficiency by defective expression of human leukocyte antigen class 1 (725136003); Bare lymphocyte syndrome type 1 (725136003); Bare lymphocyte syndrome type I (725136003); Immunodeficiency by defective expression of HLA (human leukocyte antigen) class 1 (725136003); Immunodeficiency by defective expression of human leukocyte antigen class I (725136003)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
Concept ID:
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
Genes (locations): TAP1 (6p21.32); TAP2 (6p21.32); TAPBP (6p21.32)
Monarch Initiative: MONDO:0011476
OMIM®: 604571
Orphanet: ORPHA34592


Bare lymphocyte syndrome type I (BLS I) is an inherited disorder of the immune system (primary immunodeficiency). Immunodeficiencies are conditions in which the immune system is not able to protect the body effectively from foreign invaders such as bacteria or viruses. Starting in childhood, most people with BLS I develop recurrent bacterial infections in the lungs and airways (respiratory tract). These recurrent infections can lead to a condition called bronchiectasis, which damages the passages leading from the windpipe to the lungs (bronchi) and can cause breathing problems.

Many people with BLS I also have open sores (ulcers) on their skin, usually on the face, arms, and legs. These ulcers typically develop in adolescence or young adulthood. Some people with BLS I have no symptoms of the condition.

People with BLS I have a shortage of specialized immune proteins called major histocompatibility complex (MHC) class I proteins on cells, including infection-fighting white blood cells (lymphocytes), which is where the condition got its name. [from MedlinePlus Genetics]

Additional description

MHC class I deficiency-1 (MHC1D1) is an autosomal recessive immunologic disorder characterized by the onset of recurrent and chronic bacterial sinobronchial infections in the first or second decades of life, usually with progression to bronchiectasis. Nasal polyps are commonly observed, and chronic necrotizing granulomatous lesions affecting the nasal cavity, upper respiratory tract, and/or skin, which can be severe, may develop later. Patient cells have decreased or absent expression of MHC type I (HLA class I) antigens (HLA-A, HLA-B, and HLA-C) on the cell surface, leading to the alternative designation bare lymphocyte syndrome type I (BLS type I). Some patients may be asymptomatic (Sullivan et al., 1985; summary by Maeda et al., 1985; Moins-Teisserenc et al., 1999). In an early review by de la Salle et al. (1999), only 9 well-documented cases of HLA class I deficiency with normal expression of class II molecules had been found. Contrary to MHC class II deficiency (see MHC2D1, 209920), which is characterized by the early onset of severe combined immunodeficiency (SCID), HLA class I antigen deficiencies are not accompanied by particular pathologic manifestations during the first years of life, although chronic lung disease develops in late childhood. Also in contrast to type II BLS, pathology of the gut (diarrhea) is not observed. Systemic infections have not been described in HLA class I-deficient patients. Chronic bacterial infections, often beginning in the first decade of life, are restricted to the respiratory tract and extend from the upper to the lower airway. Bronchiectasis, emphysema, panbronchiolitis, and bronchial obstruction have been described. There is a high frequency of nasal polyps and involvement of the nasal sinuses. Genetic Heterogeneity of MHC Class I Deficiency See also MHC1D2 (620813), caused by mutation in the TAP2 gene (170261), MHC1D3 (620814), caused by mutation in the TAPBP (601962) gene, and MHC1D4 (241600), caused by mutation in the B2M gene (109700). See also MHC class II deficiency (see, e.g., MHC2D1; 209920).  http://www.omim.org/entry/604571

Clinical features

From HPO
MedGen UID:
Concept ID:
Disease or Syndrome
Persistent abnormal dilatation of the bronchi owing to localized and irreversible destruction and widening of the large airways.
MedGen UID:
Concept ID:
Disease or Syndrome
Inflammation of the bronchioles.
MedGen UID:
Concept ID:
Disease or Syndrome
A subcategory of chronic obstructive pulmonary disease (COPD). It occurs in people who smoke and suffer from chronic bronchitis. It is characterized by inflation of the alveoli, alveolar wall damage, and reduction in the number of alveoli, resulting in difficulty breathing.
Recurrent bronchitis
MedGen UID:
Concept ID:
Disease or Syndrome
An increased susceptibility to bronchitis as manifested by a history of recurrent bronchitis.
Chronic sinusitis
MedGen UID:
Concept ID:
Disease or Syndrome
A chronic form of sinusitis.
Chronic otitis media
MedGen UID:
Concept ID:
Disease or Syndrome
Chronic otitis media refers to fluid, swelling, or infection of the middle ear that does not heal and may cause permanent damage to the ear.
Nasal polyposis
MedGen UID:
Concept ID:
Anatomical Abnormality
Polypoidal masses arising mainly from the mucous membranes of the nose and paranasal sinuses. They are freely movable and nontender overgrowths of the mucosa that frequently accompany allergic rhinitis.
Skin ulcer
MedGen UID:
Concept ID:
Disease or Syndrome
A discontinuity of the skin exhibiting complete loss of the epidermis and often portions of the dermis and even subcutaneous fat.
Ectopia lentis
MedGen UID:
Concept ID:
Congenital Abnormality
Dislocation or malposition of the crystalline lens of the eye. A partial displacement (or dislocation) of the lens is described as a subluxation of the lens, while a complete displacement is termed luxation of the lens. A complete displacement occurs if the lens is completely outside the patellar fossa of the lens, either in the anterior chamber, in the vitreous, or directly on the retina. If the lens is partially displaced but still contained within the lens space, then it is termed subluxation.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVMHC class I deficiency
Follow this link to review classifications for MHC class I deficiency in Orphanet.

Professional guidelines


Wang X, Schoenhals JE, Li A, Valdecanas DR, Ye H, Zang F, Tang C, Tang M, Liu CG, Liu X, Krishnan S, Allison JP, Sharma P, Hwu P, Komaki R, Overwijk WW, Gomez DR, Chang JY, Hahn SM, Cortez MA, Welsh JW
Cancer Res 2017 Feb 15;77(4):839-850. Epub 2016 Nov 7 doi: 10.1158/0008-5472.CAN-15-3142. PMID: 27821490Free PMC Article
Beutler E, Felitti V, Gelbart T, Ho N
Ann Intern Med 2000 Sep 5;133(5):329-37. doi: 10.7326/0003-4819-133-5-200009050-00008. PMID: 10979877
Poller W, Schneider-Rasp S, Liebert U, Merklein F, Thalheimer P, Haack A, Schwaab R, Schmitt C, Brackmann HH
Gene Ther 1996 Jun;3(6):521-30. PMID: 8789802

Recent clinical studies


Hanna S, Etzioni A
J Allergy Clin Immunol 2014 Aug;134(2):269-75. Epub 2014 Jul 4 doi: 10.1016/j.jaci.2014.06.001. PMID: 25001848


Hanalioglu D, Ayvaz DC, Ozgur TT, van der Burg M, Sanal O, Tezcan I
Clin Immunol 2017 May;178:74-78. Epub 2017 Feb 2 doi: 10.1016/j.clim.2017.01.011. PMID: 28161407
Hanna S, Etzioni A
J Allergy Clin Immunol 2014 Aug;134(2):269-75. Epub 2014 Jul 4 doi: 10.1016/j.jaci.2014.06.001. PMID: 25001848

Supplemental Content

Table of contents

    Clinical resources

    Practice guidelines

    • PubMed
      See practice and clinical guidelines in PubMed. The search results may include broader topics and may not capture all published guidelines. See the FAQ for details.

    Recent activity

    Your browsing activity is empty.

    Activity recording is turned off.

    Turn recording back on

    See more...