Patient 1 was a male aged 3 years and 4 months with a normal mental development. He had a developed asymmetry of the lower limbs, left-sided microdactyly and hyperthelorism. He had undergone two operations for resection of tumors in the right kidney and the liver. The routine cytogenetic analysis did not reveal any chromosomal abnormalities and showed a normal male karyotype (46,XY). Patient 2 was a female aged 9 years and 4 months with a severe mental retardation, speech de- ficiency and low intelligence (IQ 25). She had facial dysmorphism, congenital dysplasia of the pelvic joint, contractures of the ankle joints and epilepsy. There was no evidence of metabolic disorder. Cytogenetic analysis showed a normal female karyotype (46,XX). The diagnosis was “mental retardation of unclear etiology.” Patient 3 was a male aged 2 years and 7 months with severe mental retardation, lack of speaking ability, hypo tonic muscles, microcephaly and facial dysmorphism. There were no anomalies of the heart, kidneys and gastro-intestinal tract. The karyotype was normal (46,XY). The diagnosis was “malformative syndrome of unclear etiology.” Patient 4 was a female aged 13 years and 8 months with a severe mental retardation (IQ 5), epilepsy, spastic paresis of limbs and hyperactivity. There was facial dys morphism – hypertelorism and convergent strabismus, but no organ anomalies. The karyotype was normal (46,XX). The diagnosis was “malformative syndrome of unclear etiology.”