Symptoms, Development & Growth: What to Expect

While every child with 18p deletion syndrome (also called Monosomy 18p) is unique, there are common patterns in how they grow and develop ^[1][2].

Cognitive and Developmental Spectrum

There is no single “typical” cognitive outcome for children with 18p-. Instead, there is a wide spectrum of possibilities:

• Intelligence: Most children experience some degree of intellectual disability, usually in the mild to moderate range ^[3]. However, some individuals with 18p- have achieved average intellectual performance ^[1].
• Speech and Language: Speech delays are very common. Children often understand more than they can say (receptive language is often stronger than expressive language) ^[3][4].
• Social Development: There is a heightened susceptibility to autistic traits, such as challenges with social interaction or a preference for repetitive behaviors ^[5].

Physical Growth and Traits

Physical development in 18p- often includes distinct features that may become more noticeable as your child grows:

• Short Stature: Many children are shorter than their peers, often due to deficiencies in growth hormones ^[6][3].
• Facial Features: Common traits include a round face, a wide mouth, and ptosis (drooping of the upper eyelids) ^[6].
• Skeletal and Dental: You may notice dental issues like crowded teeth or differences in the shape of the jaw ^[7]. Some children also have a broad or “webbed” neck ^[6].

Neurological and Movement Risks

The nervous system is often affected by the missing genetic material. It is important to watch for:

• Tone: Many infants start with hypotonia (low muscle tone or “floppiness”), which can delay motor milestones like sitting and walking, and impact feeding early on ^[3].
• Movement Disorders: Some children develop dystonia (involuntary muscle contractions that cause twisting or repetitive movements) ^[3]. In some cases, these movement issues have been successfully managed with advanced treatments ^[8].
• Catatonia: There is a risk for catatonia, a neuropsychiatric condition where a person may become unresponsive, stop speaking, or hold unusual postures ^[3]. It is important to know that this typically presents in late adolescence or adulthood, not in early childhood. It can be triggered by systemic stress, such as a severe infection, rather than common toddler tantrums or everyday stressors ^[9].

The Transition to School Age

As your child reaches school age, their needs will shift. Early interventions will transition into an Individualized Education Program (IEP). Many children with 18p- attend school, make friends, and learn new skills, though they may require specialized academic support, continued speech therapy, and classroom accommodations ^[4].

Embracing Variability

It is essential to remember that these lists represent a “library” of possible symptoms, not a checklist for your child’s future. Because of phenotypic variability, your child may have only a few of these traits or may experience them very mildly ^[2]. Early intervention is the most effective way to support your child’s individual development and help them reach their full potential ^[4].

Return to Home Page