Coexistent mosaic monosomy 21 and fragile X syndrome in a mentally retarded male patient.

[monosomy 21]

Fragile X syndrome (FXS ) is a well-recognized mental retardation syndrome with characteristic facial features and behavioural phenotype . Monosomy 21 is a rare cytogenetic aberration for which clinical features were incompletely defined since full monosomy 21 is incompatible with life . A 5 -year -old male patient with FXS and low -grade mosaicism for full monosomy 21 (46 ,XY [96 %]/45 ,XY ,-21 [4 %]) is presented . He had lack of speech and severely impaired social skills , hyperactivity , stereotypical hand movements , a special interest towards moving colourful items and a short attention span for other objects around . He had macrocephaly , a rather long face , prominent occiput and prominent midface , retrognathia , down-slanting palpebral fissures , hypertelorism and cup-shaped , posteriorly rotated and low-set ears . Full monosomy in the aberrant cell line was proven by whole chromosome painting . FXS was previously reported to accompany sex chromosome aneuploidies ; however , to the best of our knowledge , the present patient is the first FXS patient with an aberration involving autosomes . He contributes to the current knowledge on monosomy 21 phenotype , having dysmorphic facial findings despite the concurrent phenotypic expression of the FXS . As a last conclusion , cytogenetic analysis must be done to all mentally retarded patients with minor dysmorphic features .

Diseases
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Diseases presenting "behavioural phenotype" symptom

monosomy 21

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