Retinal cone dystrophy 3B

Retinal cone dystrophy 3B is a very rare genetic disorder which is characterized by ocular anomalies. Approximately 34 cases from 20 families across the world have been described in medical literature (OMIM).^[1] This disorder is associated with autosomal recessive mutations in the KCNV2 and PDE6H genes.^[2][3]

Retinal cone dystrophy 3B
Specialty	Medical genetics
Symptoms	Ocular abnormalities
Complications	Vision impairment, colorblindness
Usual onset	Mid/late childhood-early adulthood
Duration	Life-long (most of the symptoms)
Causes	Genetic mutation
Prevention	none
Frequency	very rare, only 34 cases have been described worldwide.
Deaths	-

Presentation

People with the disorder often start showing symptoms when they are in their mid-late childhood-early adulthood, these symptoms are usually the following:^[4]

• Central scotoma
• Decreased visual acuity
• Photophobia
• Severe dyschromatopsia

Additional features include nystagmus.

Etymology

This disorder was discovered by Michaelides et al., when they described ten patients from seven families across the world. These patients had retinal cone dystrophy, abnormally high rod responses, poor central vision, photophobia, mild nystagmus (in three patients), variable degrees of nearsightedness and astigmatism, progressive loss of visual acuity and color vision, reduced color discrimination, and other ocular symptoms. The families came from the United Kingdom, Somalia, Pakistan, Iran, and the United Arab Emirates.^[5]