Blindness due to consanguineous marriages

Botulinum toxin, a neurotoxin that is widely used in neuromuscular disorders, has wide applications in Ophthalmology. Stimulated by its continued need, patient demand, and co-operation from Allergan, the Botulinum Toxin Clinic is now operational at the LV Prasad Eye Institute.

Following is a brief review of its current indications, methodology, and logistics at the Clinic.

What is Consanguinity?

Consanguinity or kinship is characterized by the sharing of common ancestors. The word is derived from the Latin consanguineus, meaning 'of common blood'. Consanguineous persons have at least one common ancestor in the preceding few generations. A consanguineous marriage is one in which two individuals related by blood, such as cousins, get married and have children.

Genes, which occur in pairs, are packages of information that we inherit from our parents. The risk of birth defects is higher in consanguineous marriages because there is a greater chance of two related individuals sharing a common harmful gene and both of them passing it on to the child.

The risk and type of birth defects in consanguineous marriages varies according to how closely the couple is related. Most consanguineous couples can have normal healthy children.

What should consanguineous couples look out for?

  • The most common defects are of the sense organs and the nervous system. 
  • The skin colour may be pink and the hair white. 
  • The eyes lack pigmentation - this is known as ocular Albinism. 
  • Squint in children 
  • Night blindness leading to Retinitis Pigmentosa
  • Photophobia, decreased visual acuity, moving eye and refractive errors

What are the diseases associated with consanguineous marriages?

Retinitis Pigmentosa is a hereditary degeneration and atrophy of the retina. It is usually progressive and leads to reduced peripheral vision that causes tunnel vision, night blindness and loss of vision. This disease affects children and young adults.

In Albinism there are defects in the pigmentation of the hair, skin and eyes. In ocular albinism, only the eyes are affected. This may be associated with photophobia (aversion to light), decreased visual acuity, nystagmus (constant jerky movement of the eyes) and refractive errors.

Anridia is a congenital condition where the iris is absent.

Coloboma of iris/choroid is the absence of either of these structures, due to developmental abnormalities.

Are there any preventive measures?

  • Avoid, as far as possible, marriages between blood relations.
  • A couple in a consanguineous marriage should go for genetic counseling when they are expecting a baby to define the risks for the fetus.
  • Marrying within the family can lead to vision problems in your children.