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

Hydrophobicity-Driven Disruption Mechanism in Kindlin-3 Induced by Leukocyte Adhesion Deficiency Mutation

Leukocyte adhesion deficiency type III (LAD-III) is caused by amino acid mutations in Kindlin-3, which result in integrin activation defects. The QW motif in the Kindlin family is particularly important for integrin activation, and the Q595P mutation in the QW motif of Kindlin-3 leads to LAD-III. However, the molecular mechanisms underlying this disruption remain unclear. In this study, we employed molecular dynamics (MD) and steered MD simulations to investigate how the pathogenic Q595P mutation in Kindlin-3 alters its interaction with β1-integrin under physiological conditions. Our results show that the Q595P mutation induces conformational changes in neighboring residues, leading to a reduction in binding affinity, specificity, and mechanical strength, primarily driven by hydrophobic changes. Specifically, the Q595P mutation disrupts the torsional dynamics of residues at the Kindlin-3 binding interface by disturbing the hydrophobic environment, weakening the hydrogen bonds that are essential for stabilizing the Kindlin-3/β1-integrin interaction under both forceful and nonforceful conditions. Additionally, it enhances nonspecific hydrophobic interactions on nonbinding surfaces, further destabilizing the overall binding. These findings provide important insights into the molecular mechanisms by which pathogenic mutations in conserved regions of Kindlin-3 lead to integrin activation defects and contribute to the pathogenesis of LAD-III.

Leukocyte adhesion deficiency type III in an infant presenting with intestinal perforation and low percentage of natural killer cells: first case report from Iran

BACKGROUND

Leukocyte adhesion deficiency III (LAD III) is a very rare autosomal recessive primary immunodeficiency characterized by recurrent infections without pus formation and bleeding syndrome of Glanzmann-type and life-threatening infections. The main etiology of this condition is variations in the FERMT3 gene, which encodes kindlin-3, an integrin-binding protein. We present a toddler with unique symptom of intestinal perforation followed by prolonged bleeding due to Glanzmann-like thrombasthenia who was diagnosed as LAD-III.

CASE PRESENTATION

This report presents a toddler with leukocyte adhesion deficiency type III (LAD III), who was diagnosed because of protracted surgical wound and gastrointestinal bleeding following surgery for small bowel perforation at the age of 16 months. The patient's history was positive for febrile episodes after vaccinations, recurrent pulmonary infections, frequent severe epistaxis and ecchymotic purpuric lesions since early infancy. The presence of severe bleeding symptoms encouraged us to consider LAD III. Accordingly, sanger sequencing was performed which identified that the patient was homozygote for mutation in exon 14 of FERMT3 gene, the gene encoding for kindlin-3. Our patient also showed low percentages of CD16 and CD56 on peripheral blood flow cytometry, an unheard finding in LAD type III.

CONCLUSIONS

LAD III should be considered in differential diagnosis of any child with recurrent infections, persistent leukocytosis, and bleeding disorders. This is the first case of LAD III presenting with intestinal perforation. The present case also showed low percentage of natural killer cells which should be followed in further studies.

A Novel Variant of the FERMT3 Gene Associated With Leukocyte Adhesion Deficiency Type III (LAD-III) in a Saudi Family: A Case Series

Leukocyte adhesion deficiency type III (LAD-III) is a rare autosomal recessive disorder characterized by immune dysfunction and bleeding tendencies. The condition arises from mutations in the FERMT3 gene, which disrupts integrin activation on leukocytes and platelets. This case study focuses on a family with consanguineous parents and multiple affected individuals spanning two generations, all diagnosed with LAD-III due to a novel homozygous mutation in the FERMT3 gene (c.1683-22_1683-19del). Clinical manifestations ranged from mild ecchymosis to severe bleeding necessitating transfusions. The proband, a two-year-old male child, presented with recurrent ecchymosis, neonatal sepsis, and thrombocytopenia. His laboratory results included leukocytosis and microcytic hypochromic anemia with normal coagulation profiles. The diagnosis of LAD-III was confirmed through whole exome sequencing that identified the homozygous FERMT3 mutation. Additionally, the proband's 15-year-old sister, who had been earlier diagnosed with Glanzmann thrombasthenia, was found to carry the same mutation, as were the proband's cousin and the cousin of his father.

LAD-III, a Mild Phenotype Resulting From a Novel Variant of FERMT3 Gene: A Case Report

Leukocyte adhesion deficiency-III (LAD-III) is a rare recessive autosomal disorder characterized by bleeding syndrome of Glanzmann-type and life-threatening infections. The main etiology of this condition is variations in the FERMT3 gene, which encodes kindlin-3, an integrin-binding protein. This protein is responsible for the activation of fibrinogen receptors and integrin-mediated hematopoietic cell adhesion. So far, only limited cases of LAD-III have been reported. This case report discusses a two-year-old male infant from the Asir region, Saudi Arabia, who was referred to the pediatric hematology service due to recurrent ecchymosis and epistaxis. He was born at full term with a history of transient tachypnea of the newborn and recurrent bronchiolitis. The patient exhibited normal platelet count and coagulation profiles alongside a familial history of bleeding disorders, including a cousin with a similar condition. The patient also presented with hypospadias and café-au-lait spots. Laboratory findings revealed anemia, microcytosis, and hypochromia indicative of iron deficiency anemia. Whole exome sequencing (WES) identified a homozygous variant of uncertain significance in the FERMT3 gene, associated with autosomal recessive LAD-III. The patient was subsequently referred to an immunology subspecialty for further investigation and bone marrow transplant preparation. This case underscores the importance of comprehensive clinical and genetic evaluations in pediatric patients with unexplained bleeding tendencies.

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.

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.

Structure, signal transduction, activation, and inhibition of integrin αIIbβ3

Integrins are heterodimeric receptors comprising α and β subunits. They are expressed on the cell surface and play key roles in cell adhesion, migration, and growth. Several types of integrins are expressed on the platelets, including αvβ3, αIIbβ3, α2β1, α5β1, and α6β1. Among these, physically αIIbβ3 is exclusively expressed on the platelet surface and their precursor cells, megakaryocytes. αIIbβ3 adopts at least three conformations: i) bent-closed, ii) extended-closed, and iii) extended-open. The transition from conformation i) to iii) occurs when αIIbβ3 is activated by stimulants. Conformation iii) possesses a high ligand affinity, which triggers integrin clustering and platelet aggregation. Platelets are indispensable for maintaining vascular system integrity and preventing bleeding. However, excessive platelet activation can result in myocardial infarction (MI) and stroke. Therefore, finding a novel strategy to stop bleeding without accelerating the risk of thrombosis is important. Regulation of αIIbβ3 activation is vital for this strategy. There are a large number of molecules that facilitate or inhibit αIIbβ3 activation. The interference of these molecules can accurately control the balance between hemostasis and thrombosis. This review describes the structure and signal transduction of αIIbβ3, summarizes the molecules that directly or indirectly affect integrin αIIbβ3 activation, and discusses some novel antiαIIbβ3 drugs. This will advance our understanding of the activation of αIIbβ3 and its essential role in platelet function and tumor development.