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Retinoblastoma

560 315 Shefali Sabharanjak

Close your eyes for 30 seconds. Now try walking around your room or home for five minutes. Bet you stumbled against furniture that you already KNOW, is in place! Can you imagine how difficult life must be for the visually challenged?? One of the ways we lose our vision is due to a cancer of the eye, called retinoblastoma, that is caused by an inheritable mutation in the RB1 gene.

Simply put, a retinoblastoma is a type of cancer that attacks the eye. What makes it worse, is the fact that 80% of retinoblastoma diagnoses occur before the age of 3: it’s a type of cancer that attacks the eyes – almost exclusively – of little children. Retinoblastoma is a “good cancer”: 90% of all cases survive into adulthood. However, the fine print is terrifying: extensive radio- or chemotherapy, a lost or severely limited childhood, the possibility of losing vision in one or, in bilateral cases, both eyes!!

The Indian Scenario

India’s retinoblastoma numbers aren’t good. Year round, India diagnoses 20% of all RB cases in the world. Of these, between 10 and 30% go on to lead functioning lives as adults; the rest are disabled for life or die. Death from RB, let alone blindness, ought not to be a reality. However, India’s masses, a majority of them rural, are mostly unaware of the disease; or, despite awareness, are usually diagnosed in the later, more devastating stages; or, despite an early diagnosis, can’t afford treatment. Lack of knowledge, lack of means, lack of access: the trifecta is poisonous, and in a relentless condition like cancer, unsurprisingly lethal.

What Causes Retinoblastoma?

A genetic disease, retinoblastoma is caused by a change, or a mutation, to the genetic code. Genetic mutations come in three basic varieties: substitutions swap one base (or a stretch) for another; insertions add a base or a stretch of bases where none previously existed; and deletions remove bases. These categories are useful from a purely visual standpoint: but what really matters is their effect on the human body. For reasons that involve 3 billion years of trial and genetic error, our genetic codes are resistant to mischief.   Most mutations do not cause a loss of function; the average human carries about 4 million mutations, and only a handful of these may, over the course of his life, cause him harm.

However, like most cancerous mutations, the one in retinoblastoma isn’t just harmful: it’s positively disfiguring. Retinoblastoma is caused by a deletion, the removal of a whole set of DNA components (see Figure 1). For more information on the process of and technology behind identifying such a deletion head over to the Strand NGS Blog that describes the clinical workflow behind diagnosing a disease like Retinoblastoma.

http://blog.avadis-ngs.com/wp-content/uploads/2017/01/FigD.png
Figure 1: A 4-base deletion. Bases 4 through 7 present in the healthy reference are deleted in the patient.

Symptoms of Retinoblastoma

Leukocoria, or cat's eye, a sign of retinoblastoma, as seen when a photograph is taken with a flash.One of the earliest signs of retinoblastoma is ‘cat’s eye’ or leukocoria that is especially seen when a photograph is taken with a flash (see accompanying photo). The normal eye looks red, as is commonly seen in most photographs. The adjacent eye shows the ‘cat’s eye’ feature. This is a sign of retinoblastoma. Other symptoms include the inability to focus both eyes in the same direction and bleeding from the eye.
Pain and difficulty in seeing are other symptoms.

Can Retinoblastoma be Inherited?

About 60% of the known retinoblastoma cases are sporadic – which means that the development of the disease is purely by chance. However, 40% of the cases are inherited – which means that the child has inherited defective RB1 genes from one or both parents. The chances of losing vision in both eyes are high for such inherited mutations.

The entire outlook on retinoblastoma is not bleak, though! An early diagnosis of retinoblastoma can help a doctor decide on the best course of treatment as well.  Genetic testing can help determine what genes are mutated (changed) and have caused the disease. Genetic tests can also help determine whether retinoblastoma runs within a family or not.

Early diagnosis and confirmation of the hereditary or sporadic nature of retinoblastoma can go a long way in restoring vision in an affected child and inform future life choices. Contact us on 1-800-1022-695 (toll-free in India) or write to us at stayaheadofcancer@strandls.com for more information.

AUTHOR

Shefali Sabharanjak

All stories by: Shefali Sabharanjak