A case of constitutional trisomy 3 mosaicism in a teenage patient with mild phenotype.

Constitutional mosaicism for trisomy 3 is extremely rare, with only a few postnatally diagnosed cases reported in the literature. We report a case of constitutional trisomy 3 mosaicism in a 16-year-old female, who presented with chronic joint pain, easy bruising, joint hypermobility and dysmorphic features, including long, thin facies, over-folded dysplastic ears, and Pierre-Robin sequence (PRS) with cleft palate. The patient was small at birth, had cleft palate repair, developed chronic joint pain at age 12, and has a history of mild leukopenia and mild thrombocytopenia. Microarray analysis was consistent with a mosaic gain of an entire chromosome 3. FISH analysis of peripheral blood and buccal cells showed the presence of the supernumerary chromosome 3 in a low percentage of cells in both tissues, suggesting that the nondisjunction event occurred prior to the germ cell layer differentiation. Since trisomy 3 has been observed somatically in lymphoma, a Hematology/Oncology consultation was provided for the patient. The oncologist's evaluation for malignancy was unremarkable. A review of findings from other trisomy 3 patients reported in the literature reveals a diverse phenotypic spectrum and does not show a correlation between the proportion of abnormal cells observed in peripheral blood and the patients' clinical features or severity. This case demonstrates that the clinical presentation of an individual with trisomy 3 is highly individualized and the clinical course is difficult to predict.