Delineation of syndromes due to partial 6q imbalances. Trisomy 6q21→qter and monosomy 6q221→qter in two unrelated patients

Two unrelated patients carrying imbalances involving the long arm of chromosome 6 are described. In the first trisomy 6q21→qter had segregated from a maternal translocation t(6;16)(q15;q24). The clinical data of the proposita are compared with those of three other published cases. A partial 6q trisomy syndrome is postulated characterized by: growth deficiency of prenatal onset, psychomotor retardation, craniofacial abnormalities (microcephalia, hypertelorism, downward slanting palpebral fissures, flattened nasal bridge, long philtrum, hypoplastic perioral features, large jaw resulting in a round appearance of the face, receding chin, malformed ears) and dysmorphic extremities contractures of limbs due to short flexor tendons, hypoplastic fingers, toes and nails). In the second case, monosomy 6q221→qter resulted from a de novo rearrangement and was responsible for mental retardation and facial dysmorphism (reduced biparietal diameter, hypotelorism, absent eyebrows, prominent nose, ptosis, receding chin, dysmorphic ears). Studies of HLA and PGM₃ segregation showed normal inheritance patterns and ruled out the location of these genes in bands 6q221→qter.