Leukocyte Adhesion Deficiency

Etiology

Primarily, leukocytes cannot escape from the blood to tissues that have been attacked by microbes. Continuous surveillance of foreign antigens by leukocyte trafficking suffers disruption as well. There are three different types of LAD[1][3]:

• Type I - in which steady adhesion of leukocyte to endothelial surfaces is defective by mutations in the CD18 gene resulting in defective or deficient beta-2 integrin
• Type II - in which there is an absence of Sialyl Lewis X of E-selectin
• Type III - in which there is a defect in kindlin-3; this impairs the integrin activation cascade - specifically, a mutation in the FERMT3 gene (11q13.1) causes this type of LAD

LAD has an autosomal recessive mode of inheritance.

• Seven new mutations in the ITGB2 gene reported, which encode the beta2 integrin family including three frameshift deletions (Tyr382fsX9, Asn282fsX41, and Lys636fsX22), two splicing (IVS4-6C>A, IVS7+1G>A) and three missense (Asp128Tyr, Gly716Ala, and Ala239Thr).[4]  

Epidemiology

Leukocyte adhesion deficiency type-1 (LAD-I) is a rare, inherited combined deficiency disorder of the immune system; it affects 1 in 1 million people annually and frequently presents with recurrent, indolent bacterial infections.[5]

The literature review of the clinical findings of patients with LAD-I reveals that recurrent infections (93.3%) and poor wound healing (86%) are the most prevalent clinical findings. A defect in CD18 (the beta subunit of the integrins) was present in all patients.[6]

Mortality for severe leukocyte adhesion deficiency-I was reported as 75% by the age of 2 years (in an initial 1988 multicenter retrospective evaluation). Patients with moderate disease  (2% to 30% CD18-expressing neutrophils) survive childhood with multiple infections affecting the skin and mucosal surfaces; documented mortality exceeds 50% by the age of 40 years.[7]

Pathophysiology

Deficiency of the following integrins: LFA-1/Mac-1, p150, and p95 cause the immunologic and clinical abnormalities seen in leukocyte adhesion deficiency. These proteins function as adhesion molecules. They are present on lymphocytes, granulocytes, monocytes, and large granular lymphocytes. LFA-1, Mac-1, and glycoprotein 150/95 have a common beta chain but have distinct alpha chains denominated M1 (Mac-1 molecule), L1 (LFA-1 molecule), and X1 (p150,95 molecules). A defect in the beta subunit is accountable for the decreased expression of LFA-1/Mac-1 polypeptide. Natural killer cell activity is not affected. The lesion is on chromosome 21, noted in some patients studied by molecular biology techniques.[8] 

Histopathology

Characteristically, a biopsy of infected tissue demonstrates inflammatory infiltrates completely devoid of neutrophils. Remnants of the umbilical cord can show a loose edematous tissue with remarkably few inflammatory cells. In contrast, there is an elevated level of peripheral blood leucocytes (over 29000/microliters) due to an impaired mobilization of leukocytes to extravascular sites of inflammation.[9]

History and Physical

The classic presentation of leukocyte adhesion deficiency is recurrent bacterial infections, neutrophil adhesion defects, and umbilical cord sloughing delays. The adhesion defects result in poor leukocyte chemotaxis, particularly the neutrophil, with an inability to form pus and neutrophilia.

Individuals with leukocyte adhesion deficiency commonly suffer from bacterial infections beginning in the neonatal period. Infections such as omphalitis, pneumonia, gingivitis, and peritonitis are common and usually life-threatening due to the inability to destroy the invading pathogens. Individuals with LAD do not form abscesses because granulocytes cannot migrate to the sites of infection.

Characteristics of patients with LAD include the following[6][10][11]:

LAD I:

• Delayed separation of the umbilical cord
• Recurrent pyogenic infections, with onset in the first weeks of life
• Infections caused meanly by Staphylococcus aureus and Pseudomonas aeruginosa
• Absent pus formation
• Periodontitis

LAD II:

• Recurrent skin infections
• Pneumonia
• Bronchiectasis
• Tuberculosis    
• Denture abnormalities
• Infections are less severe and fewer as compared to LAD I

LAD III:

• Omphalitis
• Osteoporosis like bone features
• Bleeding complications
• Hematological abnormalities, e.g., bone marrow failure

Other miscellaneous manifestations may include: 

• Vaginitis
• Peritonitis
• Osteomyelitis
• Perianal abscesses 
• Sinusitis
• Tracheobronchitis
• Necrotic soft tissue infections
• Otitis media
• Meningitis
• Graft versus host reaction
• Recurrent tonsillitis
• Conjunctivitis
• Granuloma
• Oral candidiasis
• Aphthous stomatitis
• Urinary tract infections
• Lymphocytic interstitial pneumonitis
• Glomerulonephritis
• Hemolytic-uremic syndrome
• Nail dystrophy 
• Persistent hyperinsulinemic hypoglycemia of infancy
• Pyoderma gangrenosum
• Megakaryocytic acute myeloid leukemia

Evaluation

The immunological investigation of a patient with leukocyte adhesion deficiency includes[12][13][7]:

Flow Cytometry Analysis (definitive test):

• Demonstrates the absence of functional CD18 and the associated alpha subunit molecules on the surface of leukocytes using CD11 and CD18 monoclonal antibodies (LAD I)
• Demonstrates the absence of sialyl Lewis X expression (CD15a) using a monoclonal antibody directed against sialyl Lewis X (LAD-II)

Sequence analysis using genetic testing.

• To define the exact molecular defect in the beta-2 subunit

Quantitative Serum Immunoglobulins.

• IgG
• IgM
• IgA
• IgE

Antibody Activity. 

IgG antibodies (post-immunization)

• Tetanus toxoid
• Diphtheria toxoid
• Pneumococcal polysaccharide
• Polio

IgG antibodies (post-exposure)

• Rubella
• Measles
• Varicella zoster

Detection of isohemagglutinins (IgM)

• Anti-type A blood
• Anti-type B blood

Other assays

• Test for heterophile antibody
• Anti-streptolysin O titer
• Immunodiagnosis of infectious diseases (HIV, hepatitis B and C, HTLV, and dengue)
• Serum protein electrophoresis

Blood lymphocyte subpopulations

• Total lymphocyte count
• T lymphocytes (CD3, CD4, and CD8)
• B lymphocytes (CD19 and CD20)
• CD4/CD8 ratio

Lymphocyte stimulation assays

• Phorbol ester and ionophore
• Phytohemagglutinin
• Antiserum to CD3
• Chemotaxis of human lymphocytes

Phagocytic function  

Nitroblue tetrazolium (NBT) test (before and after stimulation with endotoxin)

• Unstimulated
• Stimulated

Neutrophil mobility

• In medium alone
• In the presence of chemoattractant
• In vivo and in vitro chemotaxis of granulocytes

Complement System Evaluation

Measurement of individual components by immunoprecipitation tests, ELISA, or Western blotting

• C3 serum levels
• C4 serum levels
• Factor B serum levels 
• C1 inhibitor serum levels

Hemolytic assays

• CH50
• CH100

Complement system functional studies

• Classical pathway assay (using IgM on a microtiter plate)
• Alternative pathway assay (using LPS on a microtiter plate)
• Mannose pathway assay (using mannose on a microtiter plate)  

Microbiological studies

• Nasopharyngeal swab (testing for Rhinovirus)
• Stool (testing for viral, bacterial, or parasitic infection)
• Sputum (bacterial culture and pneumocystis PCR)
• Blood (bacterial culture, HIV by PCR, HTLV testing)
• Urine (testing for cytomegalovirus and proteinuria)
• Cerebrospinal fluid (culture, chemistry, and histopathology)

Other investigations of immunodeficiency disorders 

• Bone marrow biopsy
• Complete blood cell count    
• Blood chemistry
• Histopathological studies
• Tumoral markers
• Levels of cytokines
• Chest x-ray
• Diagnostic ultrasound
• Liver function test

Treatment / Management

• The treatment of LAD-I is an allogeneic hematopoietic stem cell transplant (HSCT). By the age of 2 years, the disease is fatal in severe cases without HSCT.[7][14][7] 
• Ustekinumab, a monoclonal antibody of the p40 subunit common to IL-12 and IL-23, had been used successfully to treat refractory periodontitis and sacral ulcer in a case report with mild LAD I.[15] However, further studies are necessary to determine safety and efficacy, particularly in patients with more severe disease.  
• Recombinant human interferon-gamma treatment has been used in LAD-I. [16]
• A trial of fucose supplementation is recommended in all patients diagnosed with LAD II[17]
• Recombinant factor VIIa is considered effective in treating and preventing severe bleeding in a child patient with LAD III [18]
• The use of prophylactic immunoglobulin therapy was successful in two patients with a severe form of LAD.[19]  
• More conservative treatment is directed against specific infectious agents. Patients are infected with common pathogenic agents but not with opportunistic ones and should respond well to antimicrobial therapy. The most common pathogens affecting patients with LAD include Proteus, Klebsiella, Staphylococcus aureus, Pseudomonas aeruginosa, and enterococci.  Early aggressive treatment should be used or given as prophylactic therapy (e.g., dental procedures).
(B3)

Differential Diagnosis

Differentials for leukocyte adhesion deficiency include the following list of disorders[20]:

• Bare lymphocyte syndrome   
• Chronic granulomatous disease
• Chediak-Higashi syndrome    
• Hyper IgE syndrome 
• All of these immunological disorders have abnormal chemotaxis and/or abnormal respiratory burst activity but can be differentiated clinically by immunohistochemistry and molecular biology techniques

Prognosis

The leukocyte adhesion deficiency prognosis varies depending on the severity of the disease; it is usually fatal before one year of age. Moderate LAD cases can live longer than the third decade of life with appropriate antimicrobial therapy. Those patients with successful allogeneic hematopoietic stem cell transplants can have a better quality of life.

Complications

The most common complications are infectious diseases affecting the skin, respiratory system, gastrointestinal system, oral cavity, and some internal organs. Leukocyte adhesion deficiency has a high mortality rate.