Atypical manifestation of LRBA deficiency with predominant IBD-like phenotype.

BACKGROUND: Inflammatory bowel diseases (IBDs) denote a heterogeneous group of disorders associated with an imbalance of gut microbiome and the immune system. Importance of the immune system in the gut is endorsed by the presence of IBD-like symptoms in several primary immunodeficiencies. A fraction of early-onset IBDs presenting with more severe disease course and incomplete response to conventional treatment is assumed to be inherited in a Mendelian fashion, as exemplified by the recent discovery of interleukin (IL)-10 (receptor) deficiency. METHODS: We analyzed a patient born to consanguineous parents suffering from severe intestinal manifestations since 6 months of age and later diagnosed as IBD. Eventually, she developed autoimmune manifestations including thyroiditis and type I diabetes at the age of 6 and 9 years, respectively. Combined single-nucleotide polymorphism array-based homozygosity mapping and exome sequencing was performed to identify the underlying genetic defect. Protein structural predictions were calculated using I-TASSER. Immunoblot was performed to assess protein expression. Flow cytometric analysis was applied to investigate B-cell subpopulations. RESULTS: We identified a homozygous missense mutation (p.Ile2824Pro) in lipopolysaccharide-responsive and beige-like anchor (LRBA) affecting the C-terminal WD40 domain of the protein. In contrast to previously published LRBA-deficient patients, the mutant protein was expressed at similar levels to healthy controls. Immunophenotyping of the index patient revealed normal B-cell subpopulations except increased CD21 B cells. CONCLUSIONS: We describe a patient with a novel missense mutation in LRBA who presented with IBD-like symptoms at early age, illustrating that LRBA deficiency should be considered in the differential diagnosis for IBD(-like) disease even in the absence of overt immunodeficiency.

Presencia de un polimorfismo de la CSP-12 relacionado consusceptibilidad a sepsis grave en una muestra de trespoblaciones colombianas / Presence of a polymorphism of the csp-12 related with susceptibility to severe sepsis in colombian individuals from three different populations

La sepsis, un síndrome de respuesta sistémica a la infección, es un problema de salud pública asociado a alta morbilidad y mortalidad alrededor del mundo. Entre los múltiples genes asociados a esta enfermedad se encuentra el gen que codifica para la caspasa-12 (csp-12), en el cual se ha identificado un polimorfismo de un sólo nucleótido (125T>C) en el exón 4 que predice una forma larga (L) de la proteína, que a su vez se ha asociado con riesgo de sepsis grave y alta mortalidad. Además, se ha demostrado que la frecuencia del alelo L es mucho mayor en poblaciones afroamericanas. Este estudio evalúa la presencia ó el polimorfismo 125T®C de la csp-12 en 128 individuos: 81 pacientes de Medellín con diagnóstico de sepsis, 23 individuos sanos de una población afroamericana del Chocó y24 individuos sanos provenientes de Medellín. En las tres poblaciones se encontraron 121 individuos homocigotos S/S (csp-12 corta) y 7 heterocigotos S/L discriminados así: 3 pacientes con diagnóstico de sepsis, 3 individuos afroamericanos y 1 de la población sana de Medellín. Nuestros resultados muestran que, a pesar de ser una muestra pequeña, en nuestra población existe el alelo L, encontrándose en mayor frecuencia en individuos afroamericanos y en una menor proporción en los mestizos, tanto pacientes como en los individuos sanos. Esto indica que la población afroamericana de Colombia podría tener mayor susceptibilidad a sepsis grave que las poblaciones mestizas, las cuales, se ha demostrado, son producto de mezcla europea, amerindia y africana, ésta última en una baja proporción. Por lo tanto, se deben efectuar estudios más amplios para un mejor entendimiento de las bases genéticas de la respuesta inmune de pacientes con sepsis, con el fin de diseñar terapias más racionales y personalizadas para prevenir este síndrome.

Sepsis, a syndrome of systemic response to infection is a major public health problem, because it is associated with high morbidity and mortality. Among the genes shown to be associated with this syndrome, there is one which encodes for caspase-12 (csp-12). Within this gene, the single nucleotide polymorphism 125T>C located in exon4, which predicts a long form of the protein, has been associated with severe sepsis and increased related mortality. On the other hand, higher frequency of allele L has been reported in African American populations. The present study evaluated the csp-12 polymorphism125T>C in 128 individuals: 81 patients with sepsis, 23 healthy African Colombian subjects and 24 healthy individuals from Medellin-Colombia. We found 121 individuals homozygous S/S (csp-12 short) in these three populations and 7 heterozygotes S/L, discriminated as follows: 3 septic patients, 3 African Colombians and 1 healthy subject from Medellin. This preliminary data suggest that the csp-12L allele is present in the Colombian population, both in African Colombians and Mestizo individuals (either septic patients or healthy individuals). Therefore, more comprehensive studies should be performed to better understand the genetic basis of the immune response of patients with sepsis in order to design more rational and personalized therapies to prevent this syndrome.