Diverse clinical features and diagnostic delay in monogenic inborn errors of immunity: A call for access to genetic testing.

BACKGROUND: Inborn errors of immunity (IEIs) are a group of conditions affecting immune system development and function. Due to their clinical heterogeneity and lack of provider awareness, patients suffer from long diagnostic delays that increase morbidity and mortality. Next-generation sequencing facilitates earlier diagnosis and treatment of IEIs, but too often patients are unable to see the benefit of this technology due to gaps in providers' knowledge regarding which patients to test and barriers to accessing sequencing. METHODS: Here, we provide detailed clinical phenotyping and describe the impact of genetic sequencing on a cohort of 43 patients with monogenic IEIs seen in a tertiary care center from 2014 to 2019. Data were abstracted from a chart review, and a panel of clinical immunologists were consulted on the impact of genetic sequencing on their patients. RESULTS: We found that our patients had significant diagnostic delays, averaging 3.3 years; had diverse manifestations of immune system dysfunction; and had demonstrated highly complex medical needs, with on average 7.9 subspecialties involved in their care and 4.9 hospitalizations prior to definitive treatment. Our results also demonstrate the benefits of genetic testing, as it provided the majority of our patients with a diagnosis, and positively impacted their treatment, follow-up, and prognosis. CONCLUSION: This paper expands the paucity of literature on genetically confirmed IEIs in North America and supports the expansion of access to genetic testing for patients with clinical features suggesting IEI, such as those presented in our cohort.

Idiopathic splenomegaly in childhood and the spectrum of RAS-associated lymphoproliferative disease: a case report.

BACKGROUND: KRAS (KRAS proto-oncogene, GTPase; OMIM: 190,070) encodes one of three small guanosine triphosphatase proteins belonging to the RAS family. This group of proteins is responsible for cell proliferation, differentiation and inhibition of apoptosis. Gain-of-function variants in KRAS are commonly found in human cancers. Non-malignant somatic KRAS variants underlie a subset of RAS-associated autoimmune leukoproliferative disorders (RALD). RALD is characterized by splenomegaly, persistent monocytosis, hypergammaglobulinemia and cytopenia, but can also include autoimmune features and lymphadenopathy. In this report, we describe a non-malignant somatic variant in KRAS with prominent clinical features of massive splenomegaly, thrombocytopenia and lymphopenia. CASE PRESENTATION: A now-11-year-old girl presented in early childhood with easy bruising and bleeding, but had an otherwise unremarkable medical history. After consulting for the first time at 5 years of age, she was discovered to have massive splenomegaly. Clinical follow-up revealed thrombocytopenia, lymphopenia and increased polyclonal immunoglobulins and C-reactive protein. The patient had an unremarkable bone marrow biopsy, flow cytometry showed no indication of expanded double negative T-cells, while malignancy and storage disorders were also excluded. When the patient was 8 years old, whole exome sequencing performed on DNA derived from whole blood revealed a heterozygous gain-of-function variant in KRAS (NM_004985.5:c.37G > T; (p.G13C)). The variant was absent from DNA derived from a buccal swab and was thus determined to be somatic. CONCLUSIONS: This case of idiopathic splenomegaly in childhood due to a somatic variant in KRAS expands our understanding of the clinical spectrum of RAS-associated autoimmune leukoproliferative disorder and emphasizes the value of securing a molecular diagnosis in children with unusual early-onset presentations with a suspected monogenic origin.

Genome-wide sequencing in acutely ill infants: genomic medicine's critical application?

Diagnostic genome-wide sequencing (exome or genome sequencing and data analysis for high-penetrance disease-causing variants) in acutely ill infants appears to be clinically useful, but the value of this diagnostic test should be rigorously demonstrated before it is accepted as a standard of care. This white paper was developed by the Paediatric Task Team of the Global Alliance for Genomics and Health's Regulatory and Ethics Work Stream to address the question of how we can determine the clinical value of genome-wide sequencing in infants in an intensive care setting. After reviewing available clinical and ethics literature on this question, we conclude that evaluating diagnostic genome-wide sequencing as a comprehensive scan for major genetic disease (rather than as a large panel of single-gene tests) provides a practical approach to assessing its clinical value in acutely ill infants. Comparing the clinical value of diagnostic genome-wide sequencing to chromosomal microarray analysis, the current evidence-based standard of care, per case of serious genetic disease diagnosed provides a practical means of assessing clinical value. Scientifically rigorous studies of this kind are needed to determine if clinical genome-wide sequencing should be established as a standard of care supported by healthcare systems and insurers for diagnosis of genetic disease in seriously ill newborn infants.

IRAK-4 deficiency as a cause for familial fatal invasive infection by Streptococcus pneumoniae.

In this Letter to the Editor we report the case of two siblings with fatal pneumococcal meningitis as the initial manifestation of IRAK-4 deficiency caused by previously undescribed mutations in IRAK4. The letter also highlights the importance of invasive pneumococcal infection as a critical 'red flag' warning of the potential for an underlying primary immunodeficiency and identifies some of the challenges in making the clinical diagnosis of IRAK-4 deficiency.

Human primary immunodeficiencies causing defects in innate immunity.

PURPOSE OF REVIEW: There have been exciting recent advances in identifying new mutations that cause human primary immunodeficiencies which impact innate immune defences. In this review, we will highlight the most important and influential advances published in the last 18 months related to the defects of the innate immune system. We will also provide clinical context to facilitate the incorporation of these discoveries into clinical practice. RECENT FINDINGS: We will specifically focus on three areas that have seen recent significant advances: defects in Toll-like receptor signalling that enhance susceptibility to viral infection, particularly herpes simplex encephalitis; defects in innate immunity that impact phagocyte function predisposing to mycobacterial infection; and the discovery of genes responsible for isolated congenital asplenia. SUMMARY: The field of innate immunodeficiency has benefited greatly from the recent improvements in genome sequencing technology and has advanced dramatically in the last 18 months. For clinicians confronted with patients with suspected innate immunodeficiency, these new discoveries not only increase the likelihood that a patient will receive a specific molecular diagnosis and tailored therapy, but also add significant complexity to the diagnostic workup. Future challenges will include identifying accurate, cost-effective diagnostic approaches to these novel immunodeficiencies, so these impressive advances in our understanding of innate immunity can be translated into improved health outcomes for our affected patients and their families.

Eighteen-year follow-up of a patient with cobalamin F disease (cblF): report and review.

Cobalamin F disease (cblF) is a rare disorder of intracellular cobalamin metabolism resulting in failure to thrive, recurrent stomatitis, skin rash, megaloblastic anemia, hypotonia, seizures, and intellectual disability. Data on long-term outcomes are not available. We report on the outcome of a patient with cblF disease with a frameshift mutation in the LMBRD1 gene after 18 years of intramuscular hydroxycobalamin treatment.

Optimizing outcomes of hematopoietic stem cell transplantation for severe combined immunodeficiency.

This FOCIS Centers of Excellence Short Analytical Review is based on the clinical vignette of two boys from the same family with very different outcomes following hematopoietic stem cell transplantation (HSCT) for X-linked severe combined immunodeficiency (SCID). We review the kinetics of immune reconstitution following HSCT in SCID and emphasize the latest information regarding optimizing transplant outcomes for this disorder. The cases illustrate the difficulties and controversies surrounding the optimal strategies for planning SCID transplants. Specifically, we will focus on 3 areas of current debate and investigation: (i) factors involved in donor selection; (ii) the role of pretransplant conditioning; and (iii) benefits of early HSCT for SCID.