SNP Shot: Genomic Insights

Retinoblastoma is a rare eye cancer that primarily affects young children, usually before age 5. It originates in the retina, the light-sensitive tissue at the back of the eye responsible for vision and color perception.

While retinoblastoma often affects only one eye, about one-third of affected children develop it in both eyes. A common early sign is leukocoria, also known as "cat's eye reflex," a visible white reflection in the pupil. This whiteness is more noticeable in low light or flash photography. Other signs can include misaligned eyes (strabismus), which may lead to squinting; changes in the iris color; redness, pain, or swelling of the eyelids; and vision impairment or blindness in the affected eye(s).

Early diagnosis of retinoblastoma is crucial, as it is often curable. If left untreated, the cancer can spread beyond the eye, becoming life-threatening.

Hereditary retinoblastoma, also known as germinal retinoblastoma, occurs when a genetic mutation is present in all cells of the body. Individuals with this type are more likely to develop cancer in both eyes and have an elevated risk of developing other cancers, including pineoblastoma (a brain tumor), osteosarcoma (bone cancer), soft tissue sarcomas (cancer of muscles, etc.), and melanoma (an aggressive skin cancer).

Inheritance:

Approximately one-third of retinoblastoma cases are hereditary, meaning the RB1 gene mutation is present in all the body's cells, including reproductive cells. Those with hereditary retinoblastoma may have a family history of the disease and can pass the mutated RB1 gene to their offspring. The remaining two-thirds of cases are non-hereditary, where the RB1 gene mutations are only found in the eye's cells and cannot be inherited.

Hereditary retinoblastoma typically follows an autosomal dominant inheritance pattern, where inheriting just one copy of the altered gene increases cancer risk. This altered RB1 gene can be inherited from a parent or arise from a new mutation in the egg, sperm, or shortly after fertilization. For retinoblastoma to develop, a second mutation in the other copy of the RB1 gene must occur in retinal cells during the person's lifetime, usually in childhood, often resulting in cancer in both eyes.

Non-hereditary retinoblastoma usually affects only one eye and has no family history. Individuals are born with two normal copies of the RB1 gene, but during early childhood, both copies of the RB1 gene in certain retinal cells develop mutations. This form is not passed on to children. However, without genetic testing, it can be difficult to determine if a retinoblastoma case in one eye is hereditary or non-hereditary.