Neurological Manifestations of Primary Immunodeficiency Diseases

Clinical, immunological, and genetic description of a Mexican cohort of patients with DOCK8 deficiency

PURPOSE

We aimed to describe the clinical, immunological, and genetic features of patients with DOCK8 deficiency (DOCK8-Def) in a tertiary care center for children.

METHODS

Retrospective chart review of patients' clinical, immunological, and genetic characteristics with DOCK8-Def. Genetic analysis was performed with targeted- or whole-exome sequencing; we also assessed DOCK8 protein expression and a lymphoproliferation assay and analyzed survival by the Kaplan-Meier method.

RESULTS

We described 11 patients from 8 unrelated kindreds. The median age at symptoms' onset was 10 months (range 1-54 months). The median follow-up time was 53.4 months (4.8-118.8). All patients presented eczema and recurrent sinopulmonary and cutaneous infections. Besides those symptoms, the most frequent manifestations were bronchiectases (8/11), food allergies (6/11), and severe infections (6/11). Infrequent characteristics were detection of CMV in bronchial lavage, C. parvum-driven sclerosing cholangitis, Takayasu vasculitis, neurological syndromes, pulmonary tuberculosis, and lymphomatoid granulomatosis.

CONCLUSION

DOCK8-Def has a broad spectrum of manifestations, including allergy, autoimmunity, inflammation, infection, and cancer. The hallmark of this inborn error of immunity is IEI-associated eczema with eosinophilia and increased IgE. Here, we report six new mutations causing human DOCK8 deficiency and symptoms previously unrecognized to occur in DOCK8-Def. Therefore, an early diagnosis of DOCK8-Def is essential to facilitate an adequate treatment such as HSCT.

Transition for adolescents with learning disabilities and an immunodeficiency

Many adolescents with immunodeficiency are diagnosed with a comorbid learning disability. The process of transition from paediatric to adult healthcare for these individuals occurs with a range of additional challenges. Due to the lack research available on immunodeficiency specifically, this article addresses a number of recommendations from the research undertaken with individuals with other chronic health conditions and learning disability. The research suggests that for individuals with learning disabilities autonomy and independence needs to be acknowledged despite their perceived need for increased input from parents and medical professionals. Instead, medical professionals could prioritise their relationship with the adolescent patient by ensuring communication needs are met and that a sense of continuity between paediatric and adult services is maintained. Families can be supported through psychological interventions which provide skills to allow family members to empower their young adult with a learning disability. Specific tools to help the transition process run more smoothly are also recommended and have proven to be effective in other parts of the world.

[Combined immunodeficiency due to DOCK8 deficiency. State of the art]

Combinedimmunodeficiency (CID) due to DOCK8 deficiency is an inborn error of immunity (IBD) characterized by dysfunctional T and B lymphocytes; The spectrum of manifestations includes allergy, autoimmunity, inflammation, predisposition to cancer, and recurrent infections. DOCK8 deficiency can be distinguished from other CIDs or within the spectrum of hyper-IgE syndromes by exhibiting profound susceptibility to viral skin infections, associated skin cancers, and severe food allergies. The 9p24.3 subtelomeric locus where DOCK8 is located includes numerous repetitive sequence elements that predispose to the generation of large germline deletions and recombination-mediated somatic DNA repair. Residual production DOCK8 protein contributes to the variable phenotype of the disease. Severe viral skin infections and varicella-zoster virus (VZV)-associated vasculopathy, reflect an essential role of the DOCK8 protein, which is required to maintain lymphocyte integrity as cells migrate through the tissues. Loss of DOCK8 causes immune deficiencies through other mechanisms, including a cell survival defect. In addition, there are alterations in the response of dendritic cells, which explains susceptibility to virus infection and regulatory T lymphocytes that could help explain autoimmunity in patients. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment; it improves eczema, allergies, and susceptibility to infections.

Phosphate Transporter Profiles in Murine and Human Thymi Identify Thymocytes at Distinct Stages of Differentiation

Thymocyte differentiation is dependent on the availability and transport of metabolites in the thymus niche. As expression of metabolite transporters is a rate-limiting step in nutrient utilization, cell surface transporter levels generally reflect the cell's metabolic state. The GLUT1 glucose transporter is upregulated on actively dividing thymocytes, identifying thymocytes with an increased metabolism. However, it is not clear whether transporters of essential elements such as phosphate are modulated during thymocyte differentiation. While PiT1 and PiT2 are both phosphate transporters in the SLC20 family, we show here that they exhibit distinct expression profiles on both murine and human thymocytes. PiT2 expression distinguishes thymocytes with high metabolic activity, identifying immature murine double negative (CD4⁻CD8⁻) DN3b and DN4 thymocyte blasts as well as immature single positive (ISP) CD8 thymocytes. Notably, the absence of PiT2 expression on RAG2-deficient thymocytes, blocked at the DN3a stage, strongly suggests that high PiT2 expression is restricted to thymocytes having undergone a productive TCRβ rearrangement at the DN3a/DN3b transition. Similarly, in the human thymus, PiT2 was upregulated on early post-β selection CD4⁺ISP and TCRαβ⁻CD4^hiDP thymocytes co-expressing the CD71 transferrin receptor, a marker of metabolic activity. In marked contrast, expression of the PiT1 phosphate importer was detected on mature CD3⁺ murine and human thymocytes. Notably, PiT1 expression on CD3⁺DN thymocytes was identified as a biomarker of an aging thymus, increasing from 8.4 ± 1.5% to 42.4 ± 9.4% by 1 year of age (p < 0.0001). We identified these cells as TCRγδ and, most significantly, NKT, representing 77 ± 9% of PiT1⁺DN thymocytes by 1 year of age (p < 0.001). Thus, metabolic activity and thymic aging are associated with distinct expression profiles of the PiT1 and PiT2 phosphate transporters.