Instabilidade cromossómica e imunodeficiência - associação essencial no diagnóstico de Síndrome de Nijmegen

Introduction: Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder that belongs to the group of chromosomal instability syndromes, more prevalent in Central and Eastern Europe.Clinical case: We describe the case of a 14-month-old boy, born to Ukrainian parents, that presented at birth with microcephaly, small to gestational age and dysmorphic facial characteristics, which became more obvious with age. The complementary study revealed spontaneous and induced chromosomal instability, with normal fetal haemoglobin and α-fetoprotein and cellular immunodeficiency. These features suggested NBS, confirmed by the identification of the founder mutation (657del5) in homozygous state, common in patients of Slavic origin.Discussion: NBS should be considered in the presence of microcephaly, typical facial features, growth retardation, chromosomal instability and immunodeficiency. The prognostic is poor due to the occurrence of frequent infections and the high incidence of cancer. Multidisciplinary follow-up and avoidance of radiation exposition are crucial.