Welcome to the CdLS Community: A Guide for Families

Receiving a diagnosis of Cornelia de Lange Syndrome (CdLS) can feel overwhelming and life-altering ^[1]. It is normal to feel a range of emotions as you begin to navigate this new reality for your child and your family. CdLS is a rare congenital (present from birth) genetic syndrome that occurs in approximately 1 in 10,000 to 30,000 births, though estimates vary ^[2][3].

It is classified as a cohesinopathy, meaning it is caused by changes in genes that help produce the cohesin complex ^[4]. This complex is a group of proteins that acts like a molecular ring, holding DNA together to help with cell division, DNA repair, and the way genes “turn on” or “off” during development ^[5]. When this process is disrupted, it affects many different systems in the body simultaneously ^[6].

Understanding the Diagnosis

In 2018, an international group of experts established a standardized way to diagnose CdLS ^[1]. Because CdLS can look very different from one child to the next, doctors often use a clinical scoring system based on physical and developmental findings to aid in diagnosis ^[7].

Features are divided into two main categories:

• Cardinal Features: These are the most characteristic signs of CdLS, such as specific facial patterns (like thick or joined eyebrows) and major limb differences ^[1].
• Suggestive Features: These are common in CdLS but can also be seen in other conditions, such as small head size (microcephaly) or general growth delays ^[1].

Under these guidelines, a clinical score of 11 or more (including at least three cardinal features) typically supports a clinical diagnosis of CdLS ^[1]. A score of 9 to 10 (with at least two cardinal features) is considered non-classic CdLS ^[1]. If a child scores 4 or higher and has at least one cardinal feature, doctors usually recommend genetic testing to investigate further ^[1]. However, the score is a clinical aid, not a definitive severity or prognosis scale. A pathogenic genetic variant can support a diagnosis even if the clinical score is lower, and the diagnosis must be interpreted by an experienced clinician ^[1].

Common Physical Hallmarks

While every child is unique, there are several physical features frequently associated with CdLS:

• Distinctive Facial Features: This often includes synophrys (eyebrows that meet in the middle), long eyelashes, a short nose with an upturned tip, and a thin upper lip with downturned corners ^[6][1].
• Growth Restriction: Children with CdLS often grow more slowly both before birth (prenatally) and after birth (postnatally) ^[6].
• Microcephaly: This is the medical term for a head size that is smaller than expected for the child’s age and sex ^[8].
• Limb Differences: These can range from very subtle (like small hands or a shortened fifth finger) to more significant differences, such as missing or shortened limbs (limb reduction defects) ^[1].
• Increased Body Hair: You may hear doctors use the term hypertrichosis (previously referred to as hirsutism), which means generalized excess body hair that is common in children with the syndrome ^[6].

The CdLS Spectrum

One of the most important things to understand is that CdLS exists on a spectrum ^[9]. In the past, doctors mostly recognized “classic” cases where the physical features were very prominent. Today, we know that many children have “non-classic” or milder forms where the features are more subtle ^[1][10].

Some children may have the characteristic facial features but no limb differences at all ^[11]. Others may have significant developmental delays while their physical growth remains closer to the typical range ^[12]. The specific gene involved can influence where a child falls on this spectrum, though these categories help guide surveillance rather than strictly determining a child’s intelligence, speech, or future independence ^[9][13].

Addressing Early Misconceptions

When you first search for information, you may encounter outdated or confusing ideas. It is helpful to clarify a few points:

• It is not your fault: Most genetic variants causing CdLS are de novo, meaning they happen by chance at the time of conception and were not caused by anything the parents did or did not do ^[6]. However, parental genetic testing and counseling are highly recommended to understand recurrence risks for future pregnancies.
• The “Classic” look is not required: A child does not need to have joined eyebrows or missing limbs to have a CdLS diagnosis ^[11][1].
• Testing can be complex: Sometimes, standard blood tests come back negative even when a child clearly has CdLS. A negative blood result does not completely exclude the syndrome. This can happen due to mosaicism, where the genetic change is present in some cells of the body but not others ^[14]. Depending on the suspected variant and clinical context, a genetics professional might discuss testing other tissues, like a cheek swab or skin cells ^[15]. A “variant of uncertain significance” (VUS) also does not establish a diagnosis on its own.
• Development is possible: While CdLS involves developmental challenges, every child has their own trajectory. Many individuals with CdLS live well into adulthood and continue to learn and gain new skills throughout their lives ^[16][3].