Why in news?
MGM Cancer Institute in Chennai performed the world's first successful pediatric bone marrow transplant on a 12-year-old girl with Bloom Syndrome.
 
About

• Bloom syndrome was first described in 1954 by Dr. David Bloom and is rare, with a notable prevalence in Ashkenazi Jewish populations. It is a severe disorder with reduced life expectancy mainly due to cancer.

• Bloom syndrome is a rare autosomal recessive genetic disorder characterized primarily by short stature, sun-sensitive skin rash, and a high predisposition to developing various types of cancer.
• It is caused by mutations in the BLM gene, which encodes a RecQ DNA helicase protein important for DNA repair, maintenance of genome stability, and prevention of excessive sister chromatid exchanges during cell division.

Key Features

• Growth deficiency: Individuals are notably smaller than average starting in utero, with growth parameters (length, head circumference, weight) below the third percentile at birth, and adult height rarely exceeding 5 feet.
• Skin abnormalities: A characteristic sun-sensitive erythematous (red and inflamed) rash typically appears on the face (especially cheeks, nose, and around lips) and other sun-exposed areas like hands and neck. This includes telangiectasias, or visible dilated blood vessels, and pigmentary changes such as hypopigmentation and hyperpigmentation.
• Facial features: Long, narrow face, prominent nose, cheeks, ears, a small lower jaw (micrognathia), and a high-pitched voice.
• Cancer predisposition: Patients have a greatly increased risk of developing cancers at an early age, often multiple types, due to genomic instability.
• Other complications: Immunodeficiency leading to recurrent infections, infertility (especially in males), diabetes, and chronic lung disease.

Cause and Pathophysiology

• Bloom syndrome results from mutations in both copies of the BLM gene located on chromosome 15q26.1. The BLM protein is part of a family of helicases that unwind DNA during replication and repair. Loss of functional BLM protein leads to defective DNA repair and chromosome instability, resulting in increased sister chromatid exchanges, chromosomal breaks, and elevated mutation rates that underlie the clinical phenotype including cancer susceptibility.

Diagnosis and Management

• Diagnosis is based on clinical features and confirmed by detecting mutations in the BLM gene. Management focuses on cancer surveillance, sun protection, treating infections, and supportive care for growth and other complications.

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