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Background: Severe congenital neutropenia type 4 (SCN4) is a rare autosomal recessive granulopoiesis disorder caused by G6PC3 gene pathogenic variants. The estimated prevalence is 1/10,000,000 people. Over 90% of patients present a syndromic form with variable multisystemic involvement, including congenital heart defects, increased visibility of superficial veins (IVSV), inflammatory bowel disease, and congenital urogenital defects as prominent symptoms. Objectives: The objective of the study was to study non-hematological phenotypic findings that suggest a clinical diagnosis of SCN4. Methods: We examined medical records of patients diagnosed with neutropenia from January 2000 to December 2020, selecting cases with non-hematologic manifestations for phenotypic description and G6PC3 gene sequencing. Results: We found 11 cases with non-hematologic features: congenital heart defects in 8, IVSV in 6, inflammatory bowel disease in 4, urogenital defects in 4, and similar facial appearance. In addition, Sanger sequencing confirmed 3 homozygous cases for the c.210delC variant, a compound heterozygous harboring this variant, and a c.199_218+1 deletion. Conclusions: Our findings of the c.210delC variant in very close geographical settings, to date, have only been reported among Mexicans, and a mutual uncommon surname in two families strongly supports a founder effect for the variant in the studied population. Furthermore, the described non-hematologic symptoms in patients with severe primary neutropenia should be explored, confirming SCN4 by investigating G6PC3 gene mutations.

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ABSTRACT Background: Severe congenital neutropenia type 4 (SCN4) is a rare autosomal recessive granulopoiesis disorder caused by G6PC3 gene pathogenic variants. The estimated prevalence is 1/10,000,000 people. Over 90% of patients present a syndromic form with variable multisystemic involvement, including congenital heart defects, increased visibility of superficial veins (IVSV), inflammatory bowel disease, and congenital urogenital defects as prominent symptoms. Objectives: The objective of the study was to study non-hematological phenotypic findings that suggest a clinical diagnosis of SCN4. Methods: We examined medical records of patients diagnosed with neutropenia from January 2000 to December 2020, selecting cases with non-hematologic manifestations for phenotypic description and G6PC3 gene sequencing. Results: We found 11 cases with non-hematologic features: congenital heart defects in 8, IVSV in 6, inflammatory bowel disease in 4, urogenital defects in 4, and similar facial appearance. In addition, Sanger sequencing confirmed 3 homozygous cases for the c.210delC variant, a compound heterozygous harboring this variant, and a c.199_218+1 deletion. Conclusions: Our findings of the c.210delC variant in very close geographical settings, to date, have only been reported among Mexicans, and a mutual uncommon surname in two families strongly supports a founder effect for the variant in the studied population. Furthermore, the described non-hematologic symptoms in patients with severe primary neutropenia should be explored, confirming SCN4 by investigating G6PC3 gene mutations.

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BACKGROUND AND OBJECTIVES: Glucose-6-phosphate catalytic subunit 3 (G6PC3) deficiency is characterized by severe congenital neutropenia with recurrent pyogenic infections, a prominent superficial venous pattern and cardiovascular and urogenital malformations caused by an alteration of glucose homeostasis, with increased endoplasmic reticulum stress and cell apoptosis. METHODS: We reviewed our patients with G6PC3 deficiency diagnosed along the last decade in Mexico; we also searched the PubMed/Medline database for the terms ('G6PC3 deficiency' OR 'Dursun syndrome' OR 'Severe congenital neutropenia type 4'), and selected articles published in English from 2009 to 2020. RESULTS: We found 89 patients reported from at least 14 countries in 4 continents. We describe five new cases from Mexico. Of the 94 patients, 56% are male, 48% from Middle East countries and none of them had adverse reactions to live vaccines; all presented with at least 1 severe infection prior to age 2. Seventy-five per cent had syndromic features, mainly atrial septal defect in 55% and prominent superficial veins in 62%. CONCLUSIONS: With a total of 94 patients reported in the past decade, we delineate the most frequent laboratory and genetic features, their treatment and outcomes, and to expand the knowledge of syndromic and non-syndromic phenotypes in these patients.

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Buscamos aqui revisar os mecanismos imunopatológicos relacionados à neutropenia congênita.O termo neutropenia congênita é utilizado para designar uma série de distúrbios neutropênicos,de caráter permanente, intermitente, grave (< 500 neutrófilos/mm3 de sangue), ou moderado(entre 500-1.500 neutrófilos/mm3 de sangue), que podem acometer pele e mucosa do tratorespiratório e gastrintestinal. Quando a neutropenia é diagnosticada, ela deve ser distinguidadas formas adquiridas, incluindo a neutropenia pós-viral e a autoimune, da forma congênita,que pode ser uma enfermidade isolada ou fazer parte de uma doença genética. Cinquenta porcento das formas congênitas de neutropenia apresentam manifestação extra-hematopoiéticacom resposta imune adaptativa normal e infecções recorrentes no início da vida. O tratamentodestes pacientes tem por objetivo o controle e a prevenção de infecções através do uso profiláticode antibióticos, e outra forma de tratamento consiste na utilização de fator estimuladorde colônia de granulócitos recombinante humano (rHUG-CSF), que aumenta o número degranulócitos, diminui o número infecções e melhora de forma significativa a sobrevida e qualidadede vida. A revisão foi realizada por levantamento bibliográfico de banco de dados obtidosatravés de pesquisa direta, LILACS, MEDLINE e capítulos de livros. A revisão literária demonstraa importância dos neutrófilos pela defesa do hospedeiro contra micro-organismos, e defeitosgenéticos que envolvem estas células acarretam maior susceptibilidade a infecções microbianasem locais como pele e mucosa do trato respiratório e gastrintestinal. Estes defeitos genéticosdos neutrófilos envolvem o seu número, função, ou ambos. Como estes defeitos envolvendofagócitos são de caráter congênito e hereditário, as crianças são os pacientes predominantes. Osneutrófilos apresentam um papel importante na imunidade inata, prevenindo o surgimento deinfecções de repetição. O tratamento com rHUG-CSF aumenta o número de granulócitos, diminuio número de novas infecções e melhora de forma significativa a sobrevida e qualidade de vida.O transplante de células-tronco hematopoiéticas é indicado em casos refratários ao tratamentocom rHUG-CSF que apresentam infecções recorrentes graves e resistência ao tratamento semdetecção de mielodisplasia/leucemia.

Here we aim to review pathogenic mechanisms related to congenital neutropenia. The termcongenital neutropenia has been used to designate a series of neutropenic disorders that canbe permanent, intermittent, severe (< 500 neutrophils/mm3) or moderate (500-1500 neutrophils/mm3), which could affect the skin and mucosa of the respiratory and gastrointestinal tracts. Whenneutropenia is diagnosed, it is necessary to distinguish between the acquired form, includingpost-viral and autoimmune neutropenia, and the congenital form, a disease that can occur eitheralone or as part of a genetic disease. Fifty percent of the congenital forms of neutropenia haveextra-hematopoietic manifestations, with normal adaptive immune response and recurrent infections in early life. Treatment of these patients focuses primarily on controlling and preventing infections through the use of prophylactic antibiotics; another treatment approach is the use of recombinant human granulocyte colony-stimulating factor (rHUG-CSF), which increases the number of granulocytes, reduces the number of infections, and significantly improves survival rates and quality of life in these patients. Papers were directly searched on the LILACS and MEDLINE database Book chapters were also reviewed. The literature reviewed underscores theimportance of neutrophils for host defense against microorganisms and the association betweengenetic defects involving these cells and an increased susceptibility to microbial infections inthe skin and mucosa of the respiratory and gastrointestinal tracts. Genetic defects may affectneutrophil number, function, or both. Because defects involving phagocytes have a congenitaland hereditary origin, children are the most common patients. Neutrophils have an importantrole in innate immunity, preventing the emergence of recurrent infections. Treatment withrHUG-CSF increases the number of granulocytes, decreases the number of new infections, andsignificantly improves survival rates and quality of life. Hematopoietic stem cell transplantationis indicated in patients refractory to rHUG-CSF treatment with severe and recurrent infectionsand resistance to treatment with no detection of myelodysplasia/leukemia.

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