Complex genomic rearrangements (CGRs) are defined as structural variants consisting of more than two breakpoint junctions in cis. This very broad definition includes single or multiple copy-number gain and losses (CNVs), inversions, intrachromosomal and interchromosomal events, resulting from a single mitotic event. A collection of CGR cases associated with human genetic diseases by our group and others, revealed genomic structural patterns for the end-products of genomic rearrangements. Such patterns include inverted triplications interspersed with duplications (DUP-TRP/INV-DUP), a CGR that can make up to 20% of pathological copy-number variants in certain disease-locus, including in cancer genomes. Disease-associated CGRs are, in general, rare, or formed de novo genome-wide triplication of MECP2 can have a more devastating clinical consequence than gene duplication therefore it may contribute to the known variable expressivity of the disease, although the relative contribution is still undefined. To investigate the contribution of CGRs to MECP2 variable expressivity and to gain insights to the mechanism of formation underlying CGRs, we applied a combination of next generation and third generation sequencing platforms (Illumina short-reads and Optical Genome Mapping and Oxford Nanopore) along with molecular cytogenetic techniques (array-comparative genomic hybridization) in a cohort of 89 MDS individuals and parents. The duplication size in this group ranges from 248 kb to 16.5 Mb, with CGRs composing 46% (41/89) of all structural variants, including 15% (14/89) triplications (5/14 involving MECP2), 10% (9/89) translocations and 10% terminal duplications, confirming that structural complexity is a prominent feature of this disease. Preliminary genotype-phenotype analyses indicate that more severely affected patients carry either translocations to autosomal chromosomes or triplications involving MECP2, implicating gene dosage as a driver of severity. In summary, our data provide evidence that CGRs are relevant disease-associated variants that generate alterations at multiple genomic levels in a single event (copy-number variants and inversions). In all, our data indicate that complementary molecular approaches are required to resolve complex genomic rearrangement structures by facilitating detection of in cis events and phasing, this approach aids interpretation of SVs with an impact in clinical care.