Malan Syndrome

The chapter discusses the clinical phenotype and the molecular abnormalities in Malan syndrome, an overgrowth condition caused by mutations in the NFIX gene. Overgrowth in Malan syndrome can be present at birth, especially in terms of large head circumference, and it continues after birth, although statural growth velocity decreases with age. The syndrome is also characterized by dysmorphic facial traits, skeletal abnormalities, intellectual disability, visual problems, and advanced bone age. This condition is allelic to another overgrowth disorder, Marshall-Smith syndrome, with which it shares several clinical features and should be considered in the differential diagnosis. The causative gene for both conditions, NFIX, encodes the nuclear factor one X-type transcription factor, which regulates the growth of several types of connective tissues.