What is Cri Du Chat Syndrome?
Cri du chat syndrome is a genetic disease caused by a missing part of chromosome 5. Its name, which means “cat cry,” comes from a main symptom: a high-pitched cry that sounds like a cat. The severity and progression of the disease can vary depending on the exact location and size of the missing part of the chromosome. This means that the physical and mental characteristics of the condition can differ based on the specific genetic changes. Typical features of this disorder include distinct facial features, delayed development, and intellectual disability.
What Causes Cri Du Chat Syndrome?
Cri-du-chat is a condition that happens when a part or all of chromosome 5p is deleted. Most of these deletions happen out of the blue. They occur randomly when reproductive cells form in the early stages of fetal development. Interestingly, 80% to 90% of these deletions are paternal, meaning they come from the father’s side. This can happen when a chromosome breaks during the formation of a sex cell, also known as a gamete.
About 10% to 15% of the cases are a result of an unbalanced parental translocation, which is when a piece of a chromosome breaks off and attaches to another chromosome. Also, the majority of cases (80% to 90%) occur due to a deletion at the end of chromosome 5, while 3% to 5% are due to a deletion that occurs within the chromosome. It’s less common, but Cri-du-chat can also happen as a result of mosaicism (which is when some cells have the deletion and others don’t), inversions (where a part of the chromosome is flipped), and ring chromosomes (where a chromosome forms a ring).
Risk Factors and Frequency for Cri Du Chat Syndrome
Cri du chat is a rare condition, but it’s one of the most frequent chromosomal disorders. It occurs in about 1 out of every 15,000 to 50,000 babies born. It’s slightly more common in baby girls than boys. We don’t have exact numbers for how common it is globally, or if it’s more common in some racial groups. We’re also not sure about the specific risk factors tied to before birth events or the age of the baby’s parents. However, there have been some reports of parents being exposed to radiation, severe nausea and vomiting during pregnancy, extreme weight loss due to lack of appetite, and serious pregnancy complications.
Signs and Symptoms of Cri Du Chat Syndrome
During the first few moments after birth, babies with this syndrome often exhibit signs such as a high-pitched, monotonous cry. This cry isn’t unique to the syndrome but is seen in some other neurological disorders as well. These babies are usually born with a lower than average weight and a smaller head size. They may suffer from lack of oxygen, weak muscle tone, and difficulties in sucking. This can result in slow growth and development in their first few years, and frequent respiratory and intestinal infections are reported as well.
Characteristic physical malformations of the face and head are common, which can include:
- A smaller than normal head (microcephaly)
- A round face shape (moon face)
- Eyes that are spaced wider apart than usual (hypertelorism)
- Folds in the inner corner of the eye (prominent epicanthic folds)
- A large nose bridge
- Mouth corners that turn downwards
- A short area between the nose and upper lip (philtrum)
- Premature graying of hair
- More horizontal wrinkles across the palm (abnormal transverse flexion creases)
Less commonly observed characteristics include:
- Eyes slanting downwards (downward slanting palpebral fissures)
- Ears set lower on the sides of the head (low-set ears)
- Narrow auditory canals
- Small skins tags in front of the ear (preauricular tags)
- Deafness
- Near-sightedness and cataracts
- Increased pupil response to certain medications (methacholine)
- Undescended testicles and abnormalities of the urinary opening (hypospadias and cryptorchidism)
As these babies grow older, some features may change:
- Early weak muscle tone may develop into unusually strong or increased muscle tension (hypertonia)
- A more distinctive small head
- An overly noticeable brow ridge (prominent supraorbital arch)
- Improper alignment of teeth (dental malocclusions)
- The round face may become narrower and longer in adulthood
The syndrome can also lead to:
- Extreme sensitivity to sound
- Heart conditions, including defects from birth
- Skin overgrowths of blood vessels (cutaneous hemangiomas)
- Abnormal kidney function
Facial and oral abnormalities include:
- A high upper mouth palate
- A small lower jaw set back from the face (mandibular microretrognathia)
- Underdevelopment of tooth enamel (enamel hypoplasia)
- Chronic gum infection (chronic periodontitis)
The developmental issues and behavior seen in these individuals include:
- Overly active behavior (hyperactivity)
- Self-harm
- Repetitive movements
- A gentle personality
- An unusual affection for objects
- A disparity between understanding others’ speech and their own ability to express themselves or communicate effectively
Testing for Cri Du Chat Syndrome
Cri du chat syndrome, a genetic disorder, can be detected during pregnancy through a test called amniocentesis. This test can reveal the absence of a part of chromosome 5, which is associated with the syndrome. Ultrasound can also be used to visually identify any structural abnormalities in the baby before birth. Some babies may show signs of a condition called mosaicism, which can be evidenced by abnormalities in the fetus and the placenta, as well as small head size and underdeveloped cerebellum.
After birth, the syndrome can be diagnosed based on specific characteristics of the baby such as a small head, low birth weight, rounded face, low muscle tone and a cry that sounds like a cat. However, the diagnosis can be challenging as the features may vary based on the exact genetic variation. In these situations, the size and the position of the missing chromosome segment can influence the severity of the condition and overall prognosis.
If there’s suspicion of Cri du chat syndrome, a test called karyotype analysis is often the first step to confirm it. If the results are inconclusive, other specialized tests like fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH), or quantitative polymerase chain reaction (PCR) can be used. These tests provide detailed information about the individual’s genes and can identify any genetic alterations.
Brain scans like MRI haven’t been widely studied in relation to Cri du chat, but when used, the most common finding is underdevelopment of a part of the brain called the pons. Other brain anomalies involving areas like the cerebellum, corpus callosum and the upper part of the brain have also been observed.
Treatment Options for Cri Du Chat Syndrome
While there’s no specific treatment for early onset cerebral damage that happens before birth, rehabilitation, particularly when started early, can help improve a patient’s prognosis and ability to adapt socially. Just after birth, physical therapy should be started within the first week to help with any swallowing or sucking difficulties. Despite these issues, breastfeeding is still possible, and intensive care is seldom needed.
Physical therapy and speech therapy are recommended to address any delays in motor skills or speech development. Regular hearing tests are warranted as these patients often have hearing loss. Surgery, special diets, and healthy lifestyle habits can also be beneficial.
Families should be involved in the patient’s care and provided information about the condition and resources available to them. In consideration of future pregnancies, they should also have access to genetic counseling services.
What else can Cri Du Chat Syndrome be?
When identifying cri du chat syndrome, doctors also need to consider and possibly rule out other conditions that may present with similar symptoms or characteristics. These may include:
- Born with multiple abnormal bodily formations (congenital anomalies)
- Other syndromes resulting from an abnormal number of chromosomes (autosomal monosomy or trisomy syndromes)
- Conditions causing intellectual disability (mental retardation syndromes)
- Patau syndrome, a rare genetic disorder
- Wolf-Hirschhorn syndrome, another type of genetic condition
It’s crucial for doctors to meticulously consider these other conditions and perform relevant tests to make an accurate diagnosis.
What to expect with Cri Du Chat Syndrome
The rates of sickness and death tend to reduce after the first few years of life. Studies have shown that 75% of deaths occur within the first month of life, and around 90% occur within the first year. It’s worth noting that the prognosis, or anticipated outcome, greatly depends on the type, size, and location of the deletion or genetic abnormality.
Early diagnosis is one of the most crucial aspects in improving the prognosis. Early intervention allows treatments to begin sooner, which enhances physical development, motor skills, and helps with adjusting socially. This early action can greatly improve the quality of life for the patient.
Possible Complications When Diagnosed with Cri Du Chat Syndrome
Cri du chat syndrome can lead to several complications such as:
- Heart or other organ defects
- Scoliosis or curvature of the spine
- Poor muscle tone
- Problems with hearing or vision
- Intellectual disabilities or learning difficulties
Preventing Cri Du Chat Syndrome
Not only do patients experience difficulties, but their families also face added stress due to the patient’s challenging behaviors. It’s essential for both patients and their families to receive support from healthcare professionals, friends, and other families going through similar experiences. Furthermore, families should keep informed about recent information on the medical condition and be given necessary resources to manage the situation.
