Genetic disorders in babies are conditions arising from changes in an individual’s genetic material, involving genes or chromosomes. Understanding these conditions helps families navigate potential health considerations for infants and access available support.
Understanding Genetic Disorders
Deoxyribonucleic acid, or DNA, is the instruction manual for the body’s development and function, found at the core of every human cell. DNA forms a double helix structure. Genes are specific segments of DNA that provide instructions for particular traits or for producing proteins, which build tissues and control bodily processes.
These genes are organized into thread-like structures called chromosomes, located within the nucleus of nearly every cell. Humans have 23 pairs of chromosomes, with one set inherited from each parent. A genetic disorder occurs when there is a change, often called a mutation or variation, in a gene’s DNA sequence, or an alteration in the number or structure of chromosomes. Such changes can disrupt gene function or protein production, leading to various health conditions.
How Genetic Disorders are Inherited
Genetic disorders can be passed down through families in several ways, depending on how the altered gene or chromosome is transmitted. Autosomal dominant inheritance occurs when only one altered copy of a gene on a non-sex chromosome is enough to cause the condition. A child has a 50% chance of inheriting the condition if one parent is affected.
Autosomal recessive inheritance requires changes in both copies of a gene on a non-sex chromosome for a condition to manifest. Parents of an affected child each carry one copy of the altered gene but do not show symptoms themselves. There is a 25% chance with each pregnancy that the child will inherit both altered copies and develop the disorder.
X-linked inheritance involves genes located on the X chromosome, one of the sex chromosomes. Males, having only one X chromosome, are more frequently affected by X-linked recessive disorders than females, who have two X chromosomes. For X-linked recessive conditions, a male needs only one altered copy of the gene, while a female needs altered copies on both X chromosomes to be affected. Chromosomal abnormalities involve an incorrect number of chromosomes, such as an extra chromosome (trisomy) or a missing one (monosomy). Down syndrome, for instance, is caused by an extra copy of chromosome 21.
Most Common Genetic Disorders in Babies
Down syndrome, also known as Trisomy 21, is a common chromosomal condition resulting from an extra copy of chromosome 21. Babies with Down syndrome often have distinct physical features like almond-shaped eyes, a flattened face, and a single crease across the palm. They may also experience developmental delays, mild to moderate intellectual disability, and sometimes congenital heart defects.
Cystic fibrosis is an inherited disorder that affects the body’s ability to produce thin, flowing mucus, instead causing thick, sticky mucus to accumulate. This buildup primarily impacts the respiratory, digestive, and reproductive systems, leading to persistent coughs, frequent lung infections, and difficulties with digestion and weight gain. Both parents must carry the specific gene variant for a child to inherit cystic fibrosis.
Sickle cell anemia is a condition affecting red blood cells, causing them to become rigid, sticky, and crescent-shaped. These abnormally shaped cells can block blood flow, leading to pain, anemia, fatigue, and potential organ damage. This disorder is more common in individuals of African, Mediterranean, and South Asian descent.
Phenylketonuria (PKU) is a rare metabolic disorder where the body cannot properly break down phenylalanine, an amino acid found in many foods. If left untreated, phenylalanine can build up in the blood and brain, leading to intellectual disability and other neurological problems. Early detection through newborn screening allows for dietary interventions to manage the condition effectively.
Tay-Sachs disease is a severe neurological disorder that leads to the progressive destruction of nerve cells in the brain and spinal cord. Symptoms appear in infancy, including seizures, muscle stiffness, and progressive loss of vision, hearing, and motor skills. This condition is caused by a gene variant that prevents the body from producing an enzyme necessary to break down fatty substances in nerve cells.
Thalassemia is a group of inherited blood disorders characterized by the body producing less hemoglobin than normal, a protein in red blood cells that carries oxygen. This can lead to anemia, fatigue, weakness, and other complications. The severity of thalassemia varies depending on the specific type and how many genes are affected.
Detecting Genetic Disorders
Early identification of genetic disorders in babies is achieved through various screening and diagnostic methods, both before and shortly after birth. Prenatal screening tests are non-invasive and assess a baby’s risk for certain genetic conditions during pregnancy. These include blood tests and ultrasounds, such as nuchal translucency measurements, which can indicate potential chromosomal abnormalities like Down syndrome.
If screening tests suggest an increased risk, diagnostic tests can provide a definitive diagnosis. These more invasive procedures include amniocentesis, where a sample of amniotic fluid is taken, and chorionic villus sampling (CVS), which involves collecting tissue from the placenta. Both methods obtain fetal cells for genetic analysis.
Newborn screening programs, often involving a “heel prick” blood test, are conducted shortly after birth, between 24 hours and five days of age. Blood is collected on a special card and analyzed for a range of rare but serious genetic and metabolic disorders, such as PKU, cystic fibrosis, and sickle cell disease. Early identification allows for prompt medical intervention, which can significantly improve a baby’s long-term health and prevent severe complications.