Background Pure distal 1q trisomy is rare and there is limited information on genotype-phenotype correlation. The common 1q trisomy phenotype attributed to the 1q42qter segment is based on a small number of patients and consists of small for gestational age, developmental delay, macrocephaly, dysmorphic features and heart defects.
Objective To clarify the genotype-phenotype correlation of pure distal 1q trisomy.
Design/method We report five patients with pure distal 1q trisomy: 1q32.2qter (patient 1), 1q41q44 (patient 2), 1q43qter (patient 5) and 1q42.13qter in two siblings (patient 3 and 4). A PubMed search was done to identify patients with trisomies distal to 1q32. Patients with pure 1q trisomies that matched the duplications found in our patients were selected.
Results Thirty-three patients have been reported with partial trisomy distal to 1q32. Only 17 patients with pure 1q trisomy matched our patients’: ten for 1q32qter, four for 1q41q44, two for 1q42qter and one for 1q43qter. Our patients presented additional features than the common 1q trisomy phenotype. Patients 1, 2, 3 and 4 have had frequent infections with normal immunological status. Patients 1, 3 and 4 had significant sleeping problems. Patients 3 and 4 have camptodactyly and patient 4 had hypertrophied cardiomyopathy. Patients 4 and 3 respectively have moderate and mild intellectual deficiency, a feature that was thought to be mostly normal distal to the 1q42 region.
Conclusions The partial 1q trisomy phenotype is constantly expanding. An improved definition allows for the identification of critical regions and better genetic counselling and follow up.
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