We report on a pair of dizygotic twins born to consanguineous parents, showing an extreme delay in skeletal maturation (roughly corresponding to the time of birth at the age of 4 10/12 years), mild metaphyseal irregularities, and normal to large stature (+ 1 to + 2 SD) with normal growth pattern, long fingers, generalized small joint hyperlaxity with flat feet, genua valga, and low normal intellectual development. This disorder was not associated with abnormal endocrine function or abnormal Ca/P metabolism. This epiphyseal disorder is compatible with autosomal recessive inheritance.