Clinical and Genetic Spectrum of a Large Cohort of Patients With Leukocyte Adhesion Deficiency Type 1 and 3: A Multicentric Study From India

Ustekinumab for pyoderma gangrenosum-like skin ulcerations in late-onset leukocyte adhesion deficiency

Background

Leukocyte adhesion deficiency type 1 (LAD-1) is a congenital immunodeficiency leading to impaired trafficking of neutrophils to inflammation sites. Solitary or multiple pyoderma gangrenosum (PG)-like skin ulcers (PGLUs) have been reported previously in 13 children (aged 0.5-19 years) with LAD-1.

Objective

Our aim was to report the case of a 10-year-old boy presenting with PGLUs as the first manifestation of LAD-1 treated with ustekinumab.

Methods

We obtained in situ cytokine profiles.

Results

PGLUs were triggered by cutaneous ringworm infection (Trichophyton tonsurans). Skin biopsy samples showed increased intralesional expression of IL-17A, Il-23, and IL-1β as compared with their expression in healthy controls. After an unsuccessful attempt at treatment with oral methylprednisolone, ustekinumab induced regression of the ulcerations, associated with complete normalization of the cytokine profile.

Conclusions

PGLUs, triggered by ringworm infection, can be a late harbinger of LAD-1. Ustekinumab is a safe and effective therapeutic option for patients with LAD-1 and PGLUs while bridging the time until stem cell transplantation.

Analysis of Clinical, Immunological and Molecular Features of Leukocyte Adhesion Deficiency Type I in Egyptian Children

PURPOSE

Leukocyte adhesion deficiency (LAD) represents a rare group of inherited inborn errors of immunity (IEI) characterized by bacterial infections, delayed umbilical stump separation, and autoimmunity. This single-center study aimed at describing the clinical, immunological, and molecular characterizations of 34 LAD-I Egyptian pediatric patients.

METHODS

Details of 34 patients' personal medical history, clinical and laboratory findings were recorded; Genetic material from 28 patients was studied. Mutational analysis was done by Sanger sequencing.

RESULTS

Omphalitis, skin and soft tissue infections with poorly healing ulcers, delayed falling of the umbilical stump, and recurrent or un-resolving pneumonia were the most common presentations, followed by chronic otitis media, enteropathy, periodontitis; and recurrent oral thrush. Persistent leukocytosis and neutrophilia were reported in all patients, as well as CD18 and CD11b deficiency. CD18 expression was < 2% in around 90% of patients. Sixteen different pathological gene variants were detected in 28 patients who underwent ITGß2 gene sequencing, of those, ten were novel and six were previously reported. Three families received a prenatal diagnosis. Patients were on antimicrobials according to culture's results whenever available, and on prophylactic Trimethoprim-Sulfamethoxazole 5 mg/kg once daily, with regular clinical follow up. Hematopoietic stem cell transplantation (HSCT) was offered for 4 patients. However due to severity of the disease and delay in diagnosis, 58% of the patients passed away in the first 2 years of life.

CONCLUSION

This study highlights the importance of early diagnosis and distribution of ITGß2 gene mutation in Egyptian children. Further molecular studies, however, remain a challenging necessity for better disease characterization in the region.

Integrins in Health and Disease-Suitable Targets for Treatment?

Integrin receptors are heterodimeric surface receptors that play multiple roles regarding cell-cell communication, signaling, and migration. The four members of the β2 integrin subfamily are composed of an alternative α (CD11a-d) subunit, which determines the specific receptor properties, and a constant β (CD18) subunit. This review aims to present insight into the multiple immunological roles of integrin receptors, with a focus on β2 integrins that are specifically expressed by leukocytes. The pathophysiological role of β2 integrins is confirmed by the drastic phenotype of patients suffering from leukocyte adhesion deficiencies, most often resulting in severe recurrent infections and, at the same time, a predisposition for autoimmune diseases. So far, studies on the role of β2 integrins in vivo employed mice with a constitutive knockout of all β2 integrins or either family member, respectively, which complicated the differentiation between the direct and indirect effects of β2 integrin deficiency for distinct cell types. The recent generation and characterization of transgenic mice with a cell-type-specific knockdown of β2 integrins by our group has enabled the dissection of cell-specific roles of β2 integrins. Further, integrin receptors have been recognized as target receptors for the treatment of inflammatory diseases as well as tumor therapy. However, whereas both agonistic and antagonistic agents yielded beneficial effects in animal models, the success of clinical trials was limited in most cases and was associated with unwanted side effects. This unfavorable outcome is most probably related to the systemic effects of the used compounds on all leukocytes, thereby emphasizing the need to develop formulations that target distinct types of leukocytes to modulate β2 integrin activity for therapeutic applications.

Immune-Related Molecules CD3G and FERMT3: Novel Biomarkers Associated with Sepsis

Sepsis ranks among the most common health problems worldwide, characterized by organ dysfunction resulting from infection. Excessive inflammatory responses, cytokine storms, and immune-induced microthrombosis are pivotal factors influencing the progression of sepsis. Our objective was to identify novel immune-related hub genes for sepsis through bioinformatic analysis, subsequently validating their specificity and potential as diagnostic and prognostic biomarkers in an animal experiment involving a sepsis mice model. Gene expression profiles of healthy controls and patients with sepsis were obtained from the Gene Expression Omnibus (GEO) and analysis of differentially expressed genes (DEGs) was conducted. Subsequently, weighted gene co-expression network analysis (WGCNA) was used to analyze genes within crucial modules. The functional annotated DEGs which related to the immune signal pathways were used for constructing protein-protein interaction (PPI) analysis. Following this, two hub genes, FERMT3 and CD3G, were identified through correlation analyses associated with sequential organ failure assessment (SOFA) scores. These two hub genes were associated with cell adhesion, migration, thrombosis, and T-cell activation. Furthermore, immune infiltration analysis was conducted to investigate the inflammation microenvironment influenced by the hub genes. The efficacy and specificity of the two hub genes were validated through a mice sepsis model study. Concurrently, we observed a significant negative correlation between the expression of CD3G and IL-1β and GRO/KC. These findings suggest that these two genes probably play important roles in the pathogenesis and progression of sepsis, presenting the potential to serve as more stable biomarkers for sepsis diagnosis and prognosis, deserving further study.

Clinical manifestations and expression of CD18 to guide the diagnosis of leukocyte adhesion deficiency type 1: Mexico experience

BACKGROUND

Leukocyte adhesion deficiency type 1 (LAD-1) is an inborn error of immunity characterized by a defect in leukocyte trafficking.

METHODS

Patients with clinical suspicion of LAD-1 were referred to our institution. Complete blood count and flow cytometric analysis, to identify the expression of CD18, CD11b, and the lymphocyte population phenotyping, were performed, and statistical analysis was completed.

RESULTS

We report clinical manifestations and immunological findings of six Mexican patients diagnosed with LAD-1. The diagnosis was based on typical clinical presentation, combined with laboratory demonstration of leukocytosis, and significant reduction or near absence of CD18 and its associated molecules CD11a, CD11b, and CD11c on leukocytes. We found atypical manifestations, not described in other countries, such as early-onset autoimmunity or infections caused by certain microorganisms.

CONCLUSIONS

Patients with LAD-1 may present with atypical manifestations, making flow cytometry an indispensable tool to confirm the diagnosis. We present the first report of LAD-1 patients in a Latin American country.

Ablation of the GDP-fucose transporter suppresses lung cancer cell proliferation and migration by reducing expression of PD-L1

Fucosylation, an important post-translational modification, is closely related to the development of tumors. In the microenvironment of lung cancer, expression of PD-L1 and fucosylation is abnormally upregulated. However, the correlation between PD-L1 expression and its fucosylation in lung adenocarcinoma (LUAD) remains unclear. The GDP-fucose transporter (GFT) is a key molecule in cellular fucosylation. To explore the correlation between fucosylation and PD-L1 expression, we knocked out the GFT-encoding gene SLC35C1 in mouse Lewis lung adenocarcinoma cells and in human H1299 lung adenocarcinoma cells. Loss of SLC35C1 impaired the phosphorylation of EGFR and its downstream target ERK. Moreover, loss of SLC35C1 up-regulated the expression of β-TrCP, a PD-L1 E3 ligase, thereby promoting the ubiquitination of PD-L1 and its subsequent degradation. The down-regulated expression of PD-L1 leads to a decline in lung cancer cell proliferation and migration. These results suggest that fucosylation partially influences LUAD tumorigenesis by regulating PD-L1 expression.

Variable CD18 expression in a 22-year-old female with leukocyte adhesion deficiency I: Clinical case and literature review

Key Clinical Message

Partial leukocyte adhesion deficiency type 1 (LAD-1) deficiency is extremely rare condition with milder infectious manifestation and immune system imbalance leads to increased risks of autoinflammatory complications, such as pyoderma gangrenosum, that can be triggered by trauma or pregnancy. In patients with spice-site ITGB2 variants, partial expression can occur due to different β2 integrin isophorms expression.

Abstract

LAD-1, OMIM ID #116920 is a rare, autosomal recessive disorder that results from mutations in the ITGB2 gene that encodes the CD18 β2 integrin subunit. According to the CD18 expression, LAD-1 is categorized as severe (<2%), moderate (2%-30%), or mild (>30%). Here, we describe a 22-year-old female, who presented with inflammatory skin disease and oral cavity, as well as respiratory tract infections during the first year of life. LAD-1 was diagnosed at the age of 2 years by low expression of CD18 (1%). Whole-exome sequencing identified homozygous c. 59-10C>A variant in the ITGB2 gene. Despite severe phenotype, the patient survived to adulthood without hematopoietic stem cell transplantation and became pregnant at the age of 20 years, with pregnancy complicated by a pyoderma gangrenosum-like lesion. During her life, CD18 expression increased from 1% to 9%; at 22 years of age, 5% of neutrophils and 9% of lymphocytes were CD18+. All CD18+-lymphocytes were predominantly memory/effector cytotoxic T cells. However, revertant mosaicism was not being established suggesting that CD18 expression variability may be mediated by other mechanisms such as different β2 integrin isophorms expression.

Clinical and Osteopetrosis-Like Radiological Findings in Patients with Leukocyte Adhesion Deficiency Type III

BACKGROUND

Leukocyte and platelet integrin function defects are present in leukocyte adhesion deficiency type III (LAD-III) due to mutations in FERMT3. Additionally, osteoclast/osteoblast dysfunction develops in LAD-III.

AIM

To discuss the distinguishing clinical, radiological, and laboratory features of LAD-III.

METHODS

This study included the clinical, radiological, and laboratory characteristics of twelve LAD-III patients.

RESULTS

The male/female ratio was 8/4. The parental consanguinity ratio was 100%. Half of the patients had a family history of patients with similar findings. The median age at presentation and diagnosis was 18 (1-60) days and 6 (1-20) months, respectively. The median leukocyte count on admission was 43,150 (30,900-75,700)/μL. The absolute eosinophil count was tested in 8/12 patients, and eosinophilia was found in 6/8 (75%). All patients had a history of sepsis. Other severe infections were pneumonia (66.6%), omphalitis (25%), osteomyelitis (16.6%), gingivitis/periodontitis (16%), chorioretinitis (8.3%), otitis media (8.3%), diarrhea (8.3%), and palpebral conjunctiva infection (8.3%). Four patients (33.3%) received hematopoietic stem cell transplantation (HSCT) from HLA-matched-related donors, and one deceased after HSCT. At initial presentation, 4 (33.3%) patients were diagnosed with other hematologic disorders, three patients (P5, P7, and P8) with juvenile myelomonocytic leukemia (JMML), and one (P2) with myelodysplastic syndrome (MDS).

CONCLUSION

In LAD-III, leukocytosis, eosinophilia, and bone marrow findings may mimic pathologies such as JMML and MDS. In addition to non-purulent infection susceptibility, patients with LAD-III exhibit Glanzmann-type bleeding disorder. In LAD-III, absent integrin activation due to kindlin-3 deficiency disrupts osteoclast actin cytoskeleton organization. This results in defective bone resorption and osteopetrosis-like radiological changes. These are distinctive features compared to other LAD types.

The Role of LFA-1 for the Differentiation and Function of Regulatory T Cells—Lessons Learned from Different Transgenic Mouse Models

Regulatory T cells (Treg) are essential for the maintenance of peripheral tolerance. Treg dysfunction results in diverse inflammatory and autoimmune diseases with life-threatening consequences. β2-integrins (CD11a-d/CD18) play important roles in the migration of leukocytes into inflamed tissues and cell signaling. Of all β2-integrins, T cells, including Treg, only express CD11a/CD18, termed lymphocyte function-associated antigen 1 (LFA-1), on their surface. In humans, loss-of-function mutations in the common subunit CD18 result in leukocyte adhesion deficiency type-1 (LAD-1). Clinical symptoms vary depending on the extent of residual β2-integrin function, and patients may experience leukocytosis and recurrent infections. Some patients can develop autoimmune diseases, but the immune processes underlying the paradoxical situation of immune deficiency and autoimmunity have been scarcely investigated. To understand this complex phenotype, different transgenic mouse strains with a constitutive knockout of β2-integrins have been established. However, since a constitutive knockout affects all leukocytes and may limit the validity of studies focusing on their cell type-specific role, we established a Treg-specific CD18-floxed mouse strain. This mini-review aims to delineate the role of LFA-1 for the induction, maintenance, and regulatory function of Treg in vitro and in vivo as deduced from observations using the various β2-integrin-deficient mouse models.

Hematologically important mutations: Leukocyte adhesion deficiency (second update)

Leukocyte adhesion deficiency (LAD) is an immunodeficiency caused by defects in the adhesion of leukocytes (especially neutrophils) to the blood vessel wall. As a result, patients with LAD suffer from severe bacterial infections and impaired wound healing, accompanied by neutrophilia. In LAD-I, characterized directly after birth by delayed separation of the umbilical cord, mutations are found in ITGB2, the gene that encodes the β subunit (CD18) of the β₂ integrins. In the rare LAD-II disease, the fucosylation of selectin ligands is disturbed, caused by mutations in SLC35C1, the gene that encodes a GDP-fucose transporter of the Golgi system. LAD-II patients lack the H and Lewis Le^a and Le^b blood group antigens. Finally, in LAD-III, the conformational activation of the hematopoietically expressed β integrins is disturbed, leading to leukocyte and platelet dysfunction. This last syndrome is caused by mutations in FERMT3, encoding the kindlin-3 protein in all blood cells, involved in the regulation of β integrin conformation. This article contains an update of the mutations that we consider to be relevant for the various forms of LAD.

[Leucocyte adhesion deficiency: detection of the first cases in Paraguay]

OBJECTIVE

To implement the diagnostic technique for LAD by evaluating the expression of CD18 and CD15 in healthy patients and in a group with clinical suspicion.

METHODS

Observational, descriptive, and cross-secctional study, carried out in pediatric patients attended in the Instituto de Investigaciones en Ciencias de la Salud, and patients from public hospitals with clinical suspicion of LAD were studied. The molecules CD18 and CD15 in peripheral blood leukocytes was evaluated by flow cytometry, establishing a normal range in healthy patients. The presence of LAD was established by decreased expression of CD18 or CD15.

RESULTS

Sixty pediatric patients were evaluated: 20 apparently healthy and 40 with clinical suspicion of leukocyte adhesion deficiency; 12 of 20 healthy patients were male (median age: 14 years) and 27 of 40 with suspected disease were female (median age: 2 years). Persistent leukocytosis and respiratory tract (32%) infections predominated. The expression range of CD18 and CD15 in healthy patients was 95%-100%, and in patients with clinical suspicion it was 0%-100%. One patient with 0% of CD18 (LAD-1) and one patient with 0% of CD15 (LAD-2) were detecte.

CONCLUSIONS

The implementation of a new diagnostic technique allowed to establish a normal range of CD18 and CD15 by flow cytometry, and it was possible to detect the first two cases of LAD in Paraguay.

Case report: HLA-haploidentical hematopoietic cell transplant with posttransplant cyclophosphamide in a patient with leukocyte adhesion deficiency type I

Leukocyte adhesion deficiency type I (LAD-I) is a rare autosomal recessive inborn error of immunity (IEI) caused by the defects in CD18, encoded by the ITGB2 gene. LAD-I is characterized by defective leukocyte adhesion to the vascular endothelium and impaired migration of leukocytes. Allogeneic hematopoietic cell transplant (HCT) is the only curative treatment for LAD-I. In an absence of ideal donor for HCT, human leukocyte antigen (HLA)-haploidentical HCT is performed. Posttransplant cyclophosphamide (PT-CY) is a relatively new graft-versus-host disease (GVHD) prophylactic measure and has been increasingly used in HLA-haploidentical HCT for malignant and nonmalignant diseases. However, experience in using PT-CY for rare IEIs, such as LAD-I, is very limited. We report a case of LAD-I successfully treated with HLA-haploidentical HCT with PT-CY. Complete chimerism was achieved, and the patient was cured. Her transplant course was complicated by mild GVHD, cytomegalovirus reactivation and veno-occlusive disease/sinusoidal obstruction syndrome, which were successfully treated. HLA-haploidentical HCT with PT-CY is a safe and effective option for patients with LAD-I when HLA-matched donors are unavailable.

Three novel homozygous ITGB2 mutations among two patients with leukocyte adhesion defect type-1: Two case reports

BACKGROUND

A leukocyte adhesion defect (LAD) is a rare primary immunodeficiency disorder. LAD type 1 (LAD-1) is the most common, which is caused by ITGB2 mutation resulting in dysfunction of β2 integrin, which impairs leukocyte adherence to the endothelium.

CASE SUMMARY

The first two cases of LAD-1 in Thailand presented with recurrent omphalitis, soft tissue infection, marked leukocytosis, and neutrophilia. One patient experienced delayed umbilical cord separation. Mutation analysis was performed by direct DNA sequencing of the ITGB2 gene. The results revealed two novel homozygous missense mutations, c.920C>T (p.Leu307Pro) in exon 8 and c.758G>A (p.Arg253His) in exon 7, and one novel homozygous nonsense mutation, c.262C>T (p.Gln88Ter) in exon 4, in the genomic DNA of the first and second patients, respectively. Heterozygous mutations were identified in the parents of both patients, suggesting a carrier status. The patients were administered intravenous antibiotics for infections with good clinical responses. Hematopoietic stem cell transplantation could not be performed due to the unavailability of matched donors. However, a significant decline in infections was observed after antibiotic prophylaxis. Several follow-up visits were conducted for both patients. They are currently 6 years old.

CONCLUSION

Molecular analysis is essential for definitive diagnosis, early treatment implementation, and prevention of LAD-1 in future pregnancy.

Targeted Gene Sanger Sequencing Should Remain the First-Tier Genetic Test for Children Suspected to Have the Five Common X-Linked Inborn Errors of Immunity

To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (54.1%). The high diagnostic rate after just one round of targeted gene SS for each of the 5 common IEI (X-linked agammaglobulinemia (XLA) 77.4%, Wiskott–Aldrich syndrome (WAS) 69.2%, X-linked chronic granulomatous disease (XCGD) 59.5%, X-linked severe combined immunodeficiency (XSCID) 51.1%, and X-linked hyper-IgM syndrome (HIGM1) 58.1%) demonstrated targeted gene SS should remain the first-tier genetic test for the 5 common X-linked IEI.

Utility of targeted next generation sequencing for inborn errors of immunity at a tertiary care centre in North India

Inborn errors of immunity (IEI) are a heterogeneous group of monogenic disorders that include primary immunodeficiency's and other disorders affecting different aspects of the immune system. Next-Generation Sequencing (NGS) is an essential tool to diagnose IEI. We report our 3-year experience in setting up facilities for NGS for diagnosis of IEI in Chandigarh, North India. We used a targeted, customized gene panel of 44 genes known to result in IEI. Variant analysis was done using Ion Reporter software. The in-house NGS has enabled us to offer genetic diagnoses to patients with IEI at minimal costs. Of 121 patients who were included pathogenic variants were identified in 77 patients. These included patients with Chronic Granulomatous Disease, Severe Combined Immune Deficiency, leukocyte adhesion defect, X-linked agammaglobulinemia, Ataxia Telangiectasia, Hyper-IgE syndrome, Wiskott Aldrich syndrome, Mendelian susceptibility to mycobacterial diseases, Hyper-IgM syndrome, autoimmune lymphoproliferative syndrome, and GATA-2 deficiency. This manuscript discusses the challenges encountered while setting up and running targeted NGS for IEI in our unit. Genetic diagnosis has helped our patients with IEI in genetic counselling, prenatal diagnosis, and accessing appropriate therapeutic options.

Understanding the Role of LFA-1 in Leukocyte Adhesion Deficiency Type I (LAD I): Moving towards Inflammation?

LFA-1 (Lymphocyte function-associated antigen-1) is a heterodimeric integrin (CD11a/CD18) present on the surface of all leukocytes; it is essential for leukocyte recruitment to the site of tissue inflammation, but also for other immunological processes such as T cell activation and formation of the immunological synapse. Absent or dysfunctional expression of LFA-1, caused by mutations in the ITGB2 (integrin subunit beta 2) gene, results in a rare immunodeficiency syndrome known as Leukocyte adhesion deficiency type I (LAD I). Patients suffering from severe LAD I present with recurrent infections of the skin and mucosa, as well as inflammatory symptoms complicating the clinical course of the disease before and after allogeneic hematopoietic stem cell transplantation (alloHSCT); alloHSCT is currently the only established curative treatment option. With this review, we aim to provide an overview of the intrinsic role of inflammation in LAD I.

A novel ITGB2 variant with long survival in patients with leukocyte adhesion defect type-I

Leukocyte adhesion deficiency is an autosomal recessive primary immunodeficiency that has been divided into three types: LAD1 (beta-2 integrin (CD18) family deficiency/defect), LAD2 (absence of fucosylated carbonhydrate ligands for selectins) and LAD3 (defective activation of all beta integrins). However, recently LAD4 has been described in cystic fibrosis patients, with a defect in integrin activation reported in monocytes. LAD-I is the most common type and prevalence of 1 in 1,000,000 live births. Clinical features of LAD patients are recurrent bacterial and fungal infections, omphalitis with delayed umbilical stump separation, significant leukocytosis especially neutrophilia during infection periods, impaired pus formation, and delayed traumatic or surgical wound healing. Flow cytometry is considered a useful tool for rapid diagnosis of the disease. The study of CD18 and CD11 (a, b, c) expression patterns in peripheral blood leukocytes helps to distinguish different phenotypes of LAD-I. In general, patients with ≥ 2% CD18 expression tend to have a less severe infection and often survive until adulthood, whereas < 2% CD18 expression often results in death in infancy. In this case report, three siblings, 10, 15, and 17 years old, diagnosed with leukocyte adhesion defect type 1 in adolescence age group, are presented.

Clinical and laboratory findings in patients with leukocyte adhesion deficiency type I: A multicenter study in Turkey

Leukocyte adhesion deficiency type I is a rare primary immunodeficiency disorder characterized by mutations in the ITGB2 gene encoding CD18. We present clinical and immunological features of 15 patients with leukocyte adhesion deficiency type 1 (LAD-1). Targeted next-generation sequencing was performed with either a primary immunodeficiency gene panel comprising 266 genes or a small LAD-panel consisting of five genes for genetic analysis. To measure the expression level of integrins on the leukocyte surface, flow cytometry analysis was performed. The median age of the patients at diagnosis was 3 (1-48) months. Eleven (73%) of the 15 patients had a LAD-1 diagnosis in their first 6 months and 14 (93%) patients had consanguineous parents. Delayed separation of the umbilical cord was present in 80% (n = 12) of the patients in our cohort, whereas omphalitis was observed in 53% (n = 8) of the patients. Leukocytosis with neutrophil predominance was observed in 73% (n = 11) patients. Nine distinct variants in the ITGB2 gene in 13 of the 15 patients with LAD-1 were characterized, two of which (c.305_306delAA and c.779_786dup) are novel homozygous mutations of ITGB2. Four unrelated patients from Syria had a novel c.305_306delAA mutation that might be a founder effect for patients of Syrian origin. Four (27%) patients underwent hematopoietic stem cell transplantation. Two patients died because of HSCT complications and the other two are alive and well. Early differential diagnosis of the patients is critical in the management of the disease and genetic evaluation provides a basis for family studies and genetic counseling.

Case Report: A Case of Leukocyte Adhesion Deficiency, Type III Presenting With Impaired Platelet Function, Lymphocytosis and Granulocytosis

Fermitin family homolog 3 (FERMT3), alternatively kindlin-3 (KIND3), is an integrin binding protein (of 667 residues) encoded by the FERMT3 gene. The molecule is essential for activating integrin α_IIbβ₃ (the fibrinogen receptor) on platelets and for the integrin-mediated hematopoietic cell (including platelets, T lymphocytes, B lymphocytes, and granulocytes) adhesion. Its defects are associated with impaired primary hemostasis, described as "Glanzmann's thrombasthenia (MIM#273800)-like bleeding problem." The defects are also associated with infections, designated as "LAD1 (leukocyte adhesion deficiency, type I; MIM#116920)-like immune deficiency." The entity that joins the impaired primary hemostasis with the leukocyte malfunction has been termed "leukocyte adhesion deficiency, type III" (LAD3, autosomal recessive, MIM#612840), representing a defective activation of the integrins β₁, β₂, and β3 on leukocytes and platelets. Here, we report a male toddler with novel compound heterozygous variants, NM_178443.2(FERMT3):c.1800G>A, p.Trp600^* (a non-sense variant) and NM_178443.2(FERMT3):c.2001del p.^*668Glufs^*106 (a non-stop variant). His umbilical cord separated at about 3 weeks of age. A skin rash (mainly petechiae and purpura) and recurrent episodes of severe epistaxis required blood transfusions in early infancy. His hemostatic work-up was remarkable for a normal platelet count, but abnormal platelet function screen with markedly prolonged collagen-epinephrine and collagen-ADP closure times. The impaired platelet function was associated with reduced platelet aggregation with all agonists. The expression of platelet receptors was normal. Other remarkable findings were persistent lymphocytosis and granulocytosis, representing defects in diapedesis due to the integrin dysfunction. The natural history of his condition, structure and sequence analysis of the variations, and comparison with other LAD3 cases reported in the literature are presented.