Marshall-Smith syndrome and Malan syndrome are caused by defect in same NFIX gene. Both these disorders are characterized by excessive and rapid physical growth, specifically in bone development (maturation), delay in attainment of developmental milestones and characteristic facial features. Both these disorders are rare with less than 80 cases reported worldwide. Both are sporadic, in that there is no family history or parental relatedness that may lead to a disorder. Both the disorders are caused by de novo mutations in the affected patient and parents are not carriers.
NFIX