Structural variation is a source of genetic variation that, in some cases, may trigger pathogenicity. Here, we describe two cases, a mother and son, with the same partial inverted duplication of the long arm of chromosome 8 [invdup(8)(q24.21q24.21)] of 17.18 Mb, showing different clinical manifestations: microcephaly, dorsal hypertrichosis, seizures and neuropsychomotor development delay in the child, and a cleft lip/palate, down-slanted palpebral fissures and learning disabilities in the mother. The deleterious outcome, in general, is reflected by the gain or loss of genetic material. However, discrepancies among the clinical manifestations raise some concerns about the genomic configuration within the chromosome and other genetic modifiers. With that in mind, we also performed a literature review of research published in the last 20 years about the duplication of the same, or close, chromosome region, seeking the elucidation of at least some relevant clinical features.

Objective: To evaluate the effects of an unbalanced inheritance in a patient, while investigating and elucidating family history. Case description: This is a case report of a patient carrying an unbalanced combination consisting of a partial trisomy of 1q42.1 and a microdeletion in 8q24.3, resulting from the segregation of the familial balanced reciprocal translocation between chromosomes 1 and 8. Comments: A genetic investigation was carried out in the family, elucidating the segregation mechanisms, possible outcomes, and inheritance lineage of this balanced translocation and its unbalanced forms. This case report was the first involving these two specific chromosomal regions.