Ptosis, Hereditary Congenital 2

See PTOS1 (178300) for a form of ptosis that has been linked to chromosome 1p.

Clinical Features

McMullan et al. (2000) analyzed a large Caucasian pedigree from the southwest of England with dominant congenital isolated ptosis and found linkage to the X chromosome. There was no evidence of blepharophimosis, epicanthus inversus, or prevailing ocular motility disorder. The ptosis was strikingly symmetric and equal in both male and female family members. Affected family members were born with bilateral ptosis which resulted in an abnormally low lid position that almost impinged on the visual axis in the primary position of gaze. Patients had minimal levator function bilaterally, associated with an absent upper-lid skin crease. They had pronounced frontalis overaction and a characteristic chin-up head posture. The best corrected visual acuity showed no evidence of amblyopia in any patient studied. The portion of the pedigree available for study spanned 4 generations with 15 affected persons.

Inheritance

No male-to-male transmission was observed by McMullan et al. (2000), including individuals unavailable for study; all 6 sons of affected men were unaffected, whereas the 4 daughters of affected men were affected.

Mapping

McMullan et al. (2000) mapped the disorder to a critical region between Xq24 and Xq27.1, with a maximum single-point LOD score of 2.88 at DXS1047 and DXS98 mapped the disorder to Xq24-q27.1.