Inverted duplicated chromosome 15 syndrome

Inverted duplicated chromosome 15 syndrome, also known as isodicentric chromosome 15 syndrome (idic(15)), tetrasomy 15q, or inv dup(15), is a rare chromosomal disorder caused by the presence of a supernumerary marker chromosome derived from chromosome 15. This extra chromosome contains an inverted duplication of the proximal region of chromosome 15q, typically including the 15q11-q13 region, which is the same region implicated in Angelman and Prader-Willi syndromes. The condition results in tetrasomy (four copies) of genes in this critical region, leading to overexpression of dosage-sensitive genes including UBE3A and genes encoding GABA receptor subunits. The syndrome primarily affects the central nervous system and is characterized by early-onset hypotonia, intellectual disability ranging from mild to severe, epilepsy (often infantile spasms that may progress to Lennox-Gastaut syndrome), speech and language delays, and autism spectrum disorder or autistic features. Motor development is also significantly delayed. Behavioral features may include poor social interaction, repetitive behaviors, and anxiety. Some individuals may have mild dysmorphic facial features, though these are often subtle and nonspecific. There is currently no cure for inverted duplicated chromosome 15 syndrome. Treatment is supportive and symptom-based, including antiepileptic medications for seizure management, speech and language therapy, occupational therapy, physical therapy, and behavioral interventions for autism spectrum features. Early intervention programs are recommended to optimize developmental outcomes. Seizures in this condition can be particularly difficult to control and may require multiple medications or specialized epilepsy management. Ongoing monitoring by a multidisciplinary team including neurologists, developmental pediatricians, and therapists is essential for comprehensive care.

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