Familial Nijmegen Breakage Syndrome Genetically Confirmed in Ukraine Provides Dermatologic Clues to Immunodeficiency

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive primary immunodeficiency characterized by microcephaly, distinctive facial features, growth delay, immune dysfunction, and a high risk of lymphoid malignancies. Two familial cases of NBS confirmed by molecular genetic testing were associated with both dermatological manifestations and severe immunodeficiency. A family (parents and two children) presented with recurrent molluscum contagiosum. Clinical, immunological (serum immunoglobulins, lymphocyte subpopulations, functional assays), and molecular genetic analyses (sequence and CNV testing of 2,525 genes) were conducted. The 16-year-old male and 9-year-old female siblings exhibited classical NBS phenotype, including microcephaly, craniofacial dysmorphism, growth delay, recurrent respiratory infections, and persistent molluscum contagiosum. Immunological evaluation revealed decreased IgG levels. Genetic testing confirmed homozygous NBN variant c.657_661del (p.Lys219Asnfs*16); both parents were heterozygous carriers. Dermatologic manifestations, such as molluscum contagiosum, may be sentinel features of immunodeficiency in NBS. Early diagnosis and genetic confirmation are essential for risk stratification, family counseling, and disease management. Recognizing cutaneous clues tp NBS may support prompt referral for immunologic evaluation in impacted pediatric patients.