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 ... 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.