XYYYY syndrome

[1] Due to the extreme rarity of the disorder, little is understood about it,[2] and the phenotype appears to be variable.

[3] XYYYY syndrome is associated with developmental and skeletal anomalies that are also observed in other sex chromosome aneuploidies.

Findings associated with the karyotype include hypertelorism (wide-spaced eyes), low-set ears, radioulnar synostosis (fusion of the long bones in the forearm), and clinodactyly (incurved pinky fingers).

[1][note 1] Though other Y-chromosome polysomy disorders are associated with tall stature,[5] this does not appear to be true in XYYYY syndrome, with recorded heights ranging from the 10th to 97th percentile.

[1] External genitalia are normal, but testicular insufficiency appears to develop during childhood and lead to adult azoospermia.