Harris et al. (1993) reported an unusual eye movement abnormality in 10 members of an English Caucasian family. The proband was a 7-year-old boy whose mother had been diagnosed with neurofibromatosis I (NF1; 162200) and who himself had ... Harris et al. (1993) reported an unusual eye movement abnormality in 10 members of an English Caucasian family. The proband was a 7-year-old boy whose mother had been diagnosed with neurofibromatosis I (NF1; 162200) and who himself had cutaneous signs of the disorder and Lisch nodules of the irides. In addition, however, he had gaze-paretic nystagmus, rebound nystagmus, and saccadic pursuit. Despite these vestibulocerebellar ocular motor signs, he had no ataxia and magnetic resonance imaging of the brain showed no abnormality. Similar eye movement abnormalities but no stigmata of NF1 were found in the father, a younger sister, and 7 other paternal relatives, whereas the mother had normal eye movements. Harris et al. (1993) concluded that the boy inherited NF1 from his mother and the eye movement abnormality, which was unrelated, from the father. The onset of the disorder was in early childhood. Seven patients who were examined showed no tremor, dizziness, consistent ataxia, or other cerebellar signs that are often associated with these oculomotor deficits, and, apart from strabismus, the patients were asymptomatic. After childhood, there appeared to be no progression; the oldest affected member was 40 years of age. Two members had been prone to falling in childhood, and 1 admitted to dizziness when tired. Harris et al. (1993) concluded that the disorder represented a benign and previously undescribed condition. The pedigree contained one instance of male-to-male transmission, suggesting autosomal dominant inheritance. Ragge et al. (2003) provided follow-up on the family reported by Harris et al. (1993). There were 14 affected members over 3 generations. An eye movement disorder began within the first 2 years of life and was characterized by poor or absent smooth pursuit, gaze-evoked nystagmus, upbeat nystagmus, and poor vestibuloocular reflex. Nine patients had strabismus, but vision was generally well preserved. The condition was nonprogressive, and only 4 affected members showed mild balance problems. The authors suggested a cerebellar origin of the defect, likely in the flocculus.