Exclusion of chromosome 9 helps to identify mild variants of acromesomelicdysplasia Maroteaux type

Acromesomelic dysplasia Maroteaux type (AMDM) is an autosomal recessive dis order belonging to the group of acromesomelic dysplasias. AMDM is character ised by severe dwarfism with shortening of the middle and distal segments o f the limbs. An AMDM gene has recently been mapped to human chromosome 9p13 -q12 by homozygosity mapping in four consanguineous families. Here, we show linkage of the disease gene to chromosome 9p13-q12 in four of five consang uineous AMDM families and its exclusion in a fifth family with two children affected with a mild form of the disease. This study suggests that genetic heterogeneity accounts for the variable clinical and radiological severity of AMDM.