Malan syndrome is an overgrowth disorder that is characterised by high birth weight, accelerated bone maturation, developmental delay and intellectual disability, facial dysmorphism including a long or triangular face, prominent forehead, depressed nasal bridge, deep set eyes, down‐slanting palpebral fissures, long philtrum, small open mouth, thin upper vermillion in a cupid bow shape, an everted lower lip and a prominent chin. Visual problems are common and include strabismus, underdeveloped optic nerve and refractive errors. These individuals have macrocephaly, marfanoid habitus, hypermobility and skeletal deformities like pectus excavatum and kyphoscoliosis. The facial phenotype partly overlaps with Sotos syndrome.
Marshall Smith syndrome is characterized by accelerated bone maturation, failure to thrive, developmental delay, and intellectual disability and characteristic facial dysmorphism including high forehead, proptosis, blue sclera, short nose, midface hypoplasia and micrognathia. These individuals also have hypertrichosis and gingival hypertrophy and are prone for fractures due to low bone density, respiratory problem due to laryngomalacia and spinal deformities like kyphoscoliosis.
Advanced bone age, spinal deformities, intellectual disability and corpus callosal abnormality are common to both these allelic disorders. Patients with phenotypic overlap of both the disorders have also been reported. Behavioral problems, autistic features and speech delay are seen in Malan syndrome.
Malan syndrome has a milder phenotype but Marshall smith syndrome, on the other hand, have severe growth failure and early death
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