diploid-triploid mosaicism

Diploid-triploid mosaicism is a chromosomal disorder in which some cells have the usual 46 chromosomes while others have 69 chromosomes, leading to a mosaic pattern. This condition affects multiple systems and is characterized by features such as facial asymmetry, truncal obesity, and hypotonia. Although exact prevalence data are not available, the disorder is understood to be rare. The diagnosis requires analysis of tissues other than blood due to the specific distribution of abnormal cells.

Individuals with diploid-triploid mosaicism may display a range of physical and developmental features. Common findings include truncal obesity, facial asymmetry, weak muscle tone, and distinctive facial features such as malformed low-set ears and micrognathia. Additional features can include syndactyly (fusion or webbing of the fingers and toes), differences in skin pigmentation, and variable intellectual disabilities that can range from mild to more severe. Not all individuals experience every feature, and the severity of symptoms can vary considerably.

The underlying cause of diploid-triploid mosaicism is not linked to a single gene mutation but rather to the presence of two different cell populations—one with a normal diploid set and one with an extra set of chromosomes. This mosaic pattern results from an error during early cell division and is not inherited from the parents. Because no specific gene has been implicated, the precise genetic and environmental factors remain under investigation. Families are encouraged to seek genetic counseling to better understand potential implications for future pregnancies.

Currently, management of diploid-triploid mosaicism focuses on supportive care and symptom management, as there are no specifically approved treatments for this condition. Treatment is highly individualized and often involves a multidisciplinary team to address developmental, physical, and supportive care needs. Patients and families are encouraged to discuss available options with their healthcare team, and genetic counseling can provide additional guidance and support regarding long-term management.

The outlook for individuals with diploid-triploid mosaicism varies widely, reflecting the diversity in clinical presentation and severity. The condition is lifelong, and while some individuals may experience stabilization of symptoms over time, others may face ongoing challenges. Outcomes described in medical literature continue to evolve as standards of care improve, and variability in symptom severity means that each individual’s course is unique. Families often find it helpful to connect with genetic counselors and specialized care teams to explore management strategies and resources tailored to their needs.