Chromosome 18 Clinical Management Guides

Distal 18q-
Treatment and Surveillance

ICD-10 = Q99.9 or Q93.89

These recommendations are inclusive of the entire population of people with Distal 18q deletions even though each person has a unique deletion. Therefore each person’s deletion could have different genes that are hemizygous. The specific hemizygous genes for an individual patient will dictate the probability of particular phenotypes. Guidance for creating an individualized plan for evaluation and management based on the person’s specific deletion can be found in the next section. However, the information in this document encompasses the global distal 18q- evaluation and management plan.

Potential conditions in a neonate

  • Structural
    • Hernias (inguinal, umbilical)
    • Cryptorchidism, chordee, and hypospadias
      in >50% of males
    • Palate abnormality
  • Functional
    • Respiratory and feeding difficulties
    • Hypotonia
  • Biochemical
    • Jaundice

Initial evaluations after diagnosis

Referrals to

Closely monitor and manage

  • Failure to thrive/growth failure
    • Weight gain
    • Linear growth
  • Sinus/ear infections
  • Genitourinary
    • Reflux
  • Immunology/Rheumatology
    • IgA deficiency
    • Atopic disorders
    • Arthritis
    • Other autoimmune conditions
  • Neurology
    • Seizure disorder
    • Intention tremors
    • Hypotonia
  • Orthopedics
    • Scoliosis or kyphosis
  • Development
    • Milestones
    • School performance
  • Behavioral/mood changes
  • Annual Screenings
    • Thyroid
    • Vision
    • Hearing


    Potential conditions in a neonate:

    • Structural
      • Hernias (inguinal, umbilical)
      • Cryptorchidism, chordee, and hypospadias in >50% of males
      • Palate abnormality
        • >40% with abnormalities, including: high, narrow, wide, bifid uvula, submucus cleft, cleft palate alone or cleft lip and palate.
    • Functional
      • Respiratory and feeding difficulties
      • Hypotonia
    • Biochemical
      • Jaundice

    Initial Evaluations:

    • Cardiology
      • 29% had a cardiac abnormality and of those
        • 43% has an ASD or VSD
        • 38% had pulmonic stenosis.
        • No definitive region of the chromosome is associated with  CHD implying there is more than one gene on 18q impacting the development of the heart.
      • The actual incidence of heart defects may be higher as ultrasound and ECG evaluations have not been consistently been performed on all affected individuals.
    • Orthopedics
      • 74% have a foot deformation:
        • Clubfoot, vertical talus, metatarsus adductus, pes planus or pes cavus.
      • The critical region for vertical talus is between 73 and 75.5 Mb
      • Scoliosis or kyphosis –possibly related to hypotonia
    • Audiology
      • Within the total population of people with 18q deletions:
        • 49.5% had conductive hearing loss
        • 28% had sensorineural hearing loss
      • 78% of individuals whose deletion includes the TSHZ1 gene at 73 Mb  have ear canal stenosis/atresia often leading to conductive hearing loss.
    • Otolaryngology
      • Aural atresia/stenosis common
      • Middle ear effusion common
      • Normal pinnae
    • Thyroid levels
      • 15% have developed thyroid dysfunction, often at <10 years of age
        • Antibody positive hypothyroidism is the most common, by far
        • Hyperthyroidism has been reported
    • Renal ultrasound
      • 25%  with a deletion  including  the region from 73.1 – 75.1 Mb have a renal malformation
    • Ophthalmology
      • Strabismus 40%, nystagmus 29 % , myopia 35%
      • Nystagmus critical region is from 72.6-75.1 Mb
    • Genitourinary
      • Infants with genital abnormalities should be evaluated by a pediatric urologist in the first month of life. Treatment should be initiated on the same timetable as would be used for typical infants
    • Neurology
      • MRI findings:
        • 97%  have CNS dysmyelination (i.e. delayed myelination ), although 100 % of those individuals missing a region between 74.3 and 73.5 Mb have dysmyelination, it is not a progressive degenerative condition.
        • 47% Paranasal Sinus Disease (Maxillary or Ethmoid sinusitis)
        • 26% Mastoiditis
        • 34% Enlargement of Ventricular System (possibly related to brain hypoplasia; corpus callosum hypoplasia or white matter loss) 
        • 32% Delayed maturation of Occipital lobes 
        • 14% Brain abnormal signals
        • 14% Corpus Callosum abnormalities (thinner, smaller, partial or total agenesis)
        • 14% Iron deposition
        • 6% Pituitary gland abnormalities
        • 3%Virchow-Robin Perivascular spaces
        • 2.5% Deep white matter ischemia
        • 1.7% Periventricular Leukomalacia
        • 1.7% Dandy-Walker variant
        • 1.7% Chiari I malformation

    Referrals to:

    • Genetics Follow-up
      • Genetics follow-up may be  necessary if parental chromosomes have not been evaluated to rule out inherited rearrangement. 3% of the participants in our study have a parent with a balanced rearrangement. Even if no other children are planned, if one parent has a balanced rearrangement then their other children or the siblings of that parent are a risk for having the same rearrangement and consequently have a very high risk of passing on an unbalanced chromosome compliment.
      • A genetics follow-up may also be indicated if the original diagnosis was performed using cytogenetic techniques or low resolution microarray technology. A high resolution SNP or CGH microarray can determine exactly which genes are involved in the deletion. This information will become increasingly important over time as  gene-specific interventions are developed.
    • Early intervention/developmental services
      • All children with chromosome 18 abnormalities are at significant risk for developmental delay.  Prompt referral to a program the includes physical, occupational and speech therapy is important in order maximize their development.
      • 100% have developmental delay
        • 91% have speech problems
        • 32% articulation
        • 17% non-verbal
        • 18% delayed speech development
        • 7% apraxia
        • 26% not-specified
      • 79% have hypotonia
      • 68% have an intellectual disability
    • Referral to Chromosome 18 Registry & Research Society
      • The Chromosome 18 Registry is a parent support organization that provides  family members with the opportunity to meet and learn from those who have gone before them.  These are complex conditions to manage even in the least affected children making the establishment of a network of support a crucial component for maximizing the affected child’s potential. The Registry has annual national and international conferences, regional get-togethers and social media outlets, all with programs for parents, siblings and affected  adults.  The Registry works closely with and financially supports the Chromosome 18 Clinical Research Center
    • Referral to the Chromosome 18 Clinical Research Center
      • The goal of the Chromosome 18 Clinical Research Center is to make the chromosome 18 abnormalities the first treatable chromosome abnormalities. Anyone with any chromosome 18 abnormality is eligible to enroll and encouraged to enroll. Once enrolled, participants have the opportunity to  be involved in longitudinal studies of developmental progress, and when available, other studies  that could include surveys or treatment trials.  Families enrolled in the Research Center will also be the first to know new information about the conditions when it becomes available. Enrollment is a key part of proactive clinical management.

    Closely monitor and manage:

    • Failure to thrive/ growth failure
      • Weight gain
        Due to their hypotonia, suckling or feeding may be more difficult for the child. In addition, many affected children have gastroesophageal reflux, which increases not only their risk for aspiration, but also for pain, discomfort or emesis after feeding.  Children <3 years who are failing to meet expected rates of weight gain, they should be evaluated for reflux and potentially for placement of a feeding tube
      • Linear growth
        • 64% are short (<2SD) and the majority are growth hormone deficient
        • IGF1 and IGFBP3 are not definitive tests for GH deficiency in these children
        • Children that are failing to grow linearly (length or height) at expected rates for age and sex should be tested using growth hormone stimulation  (provocative) testing. This testing is typical done by a pediatric endocrinologist.
        • All treated individuals responded to GH replacement therapy (0.3 mg/kg/week) with rates of growth comparable to children with classical isolated GH deficiency
    • Sinus/ear infections
      • Due to abnormal midface architecture, affected children are at increased risk of otitis media and sinusitis.  Many have atretic or stenotic ear canals, making visual inspection difficult.  In addition, they often do not present with the typical signs of a sinus or ear infection. Therefore there should be a high index of suspicion of sinus infections when there are behavioral changes which then dictate a  longer duration of antibiotic treatment; recommendations are 10 days for otitis media, and 14 days for sinusitis.
    • Genitourinary
      • Renal anomalies and ureteral reflux are more frequent in children with distal 18q.  Affected children should have a renal ultrasound at the time of initial evaluation and referral to an pediatric nephrologist or urologist if abnormalities are noted.  Affected children who have recurrent urinary track or kidney infections  should have urodynamic studies
    • Immunology/Rheumatology
      • Immunodeficiency – 18%
        • IgA deficiency – most common
          • The exact gene responsible has not been identified but it is known to be within a region between 62.5 and 76.9 Mb (Linnankivi et al., 2006). Only persons with a deletion including this region have this risk for this condition.
    • Hypersensitivity
      • Asthma, Allergic rhinitis, Food Allergy, Atopic Dermatitis (Eczema) – 41%
    • Autoimmune conditions – 41%
      • Thyroid disease -16%
      • Skin /hair conditions -12%
      • Arthritis-4%
      • Other conditions – Lupus, Sjogren’s, Diabetes
    • Neurology
      • 96% have decreased reflexes
      • 79% have hypotonia
      • 68% have gait abnormalities
      • 62% have tremors
      • 38% have a seizure disorder. Average age at onset = 5 yrs., range = neonate to 27 yrs.
        • The seizures are treated with anticonvulsants medications. Sometimes more than one medication is needed to control seizures.  Usually , but not always, the seizures are under control while on medications. 34 (67%) out of 51 diagnosed with seizures had no seizure relapse for >12 month. The most common medication used was Valproic acid (Depakene or Depakote) followed by Carbamazepine (Tegretol); Levatiracetam (Keppra); Oxcarbazepine (Trileptal).
    • Orthopedics
      • 7% develop Scoliosis or kyphosis
    • Development
      • There are two broad groups of people with distal 18q deletions; those with deletions that include the TCF4 gene and those whose deletion does not include TCF4. People whose distal 18q deletion does not include TCF4 have IQ scores from above normal to mild intellectual disability. Those whose deletion includes TCF4 generally do not develop skills beyond that of a typical 18 month old.
    • Milestones
      • For those children whose deletion does not include the TCF4 gene, milestones are delayed but they are achieved. (Cody et al., 2013).
      • School performance
    • Behavioral/mood changes
      • 73%  have a lifetime risk of a mood disorder
      • 64% have an anxiety disorder
      • 63% have at least some autistic features
      • 37% with an ADHD diagnosis
      • 36% with other externalizing disorders
    • Annual Screenings
      • Thyroid hormone and TSH
      • Vision
      • Hearing
        • 70% have hearing loss – Conductive, sensorineural or mixed
    • Early Death
      • In the group with deletions that include the TCF4 gene, 25% died. The ages at death were between 22 months and 32 years, primarily due to complications from aspiration.
      • In the group whose deletion did not include the TCF4 gene, only 1.7% have died. The age at death was between 12 and 32 years and was sudden and unexpected in all cases.

    There is no reason to think that they are at increased risk for surgical or anesthesia complications although they may need increased monitoring due to hypotonia.

    Cody JD, Hasi M, Soileau B, Heard P, Carter E, Sebold C, O’Donnell L, Perry B, Stratton RF, Hale DE.  (2014) Establishing a reference group for distal 18q-: Clinical description and molecular basis. Hum Genet 133:199-209, doi: 10.1007/s00439-013-1364-6.


    Cody JD, Heard PL, Crandall AC, Carter EM, Li J, Hardies LJ, Lancaster J, Perry B, Stratton RF, Sebold C, Schaub RL, Soileau B, Hill A, Hasi M, Fox PT, Dale DE.  (2009)  Narrowing critical regions and determining penetrance for selected 18q– phenotypes.  Am J Med Genet 149A:1421–1430, doi:10.1002/ajmg.a.32899.


    Cody JD, Carter EM, Sebold C, Heard PL, Hale DE.  (2009)  A gene dosage map of chromosome 18: a map with clinical utility.  Genet Med 11:778–782, doi:10.1097/GIM.0b013e3181b6573d.


    Daviss WB, O’Donnell L, Soileau BT, Heard P, Carter E, Pliszka S, Gelfond JAL, Hale DE, Cody JD.  (2013) Mood disorders in individuals with distal 18q deletions.  Am J Med Genet Part B  162B:879-888, doi: 10.1002/ajmg.b.32197.


    Hasi M, Soileau B, Sebold C, Hill A, Hale DE, O’Donnell L, Cody JD. (2011) The role of the TCF4 gene in the phenotype of individuals with 18q segmental deletions. Hum Genet 130:777–787, doi:10.1007/s00439-011-1020-y.


    Heard PL, Carter EM, Crandall AC, Sebold C, Hale DE, Cody JD.  (2009)  High resolution genomic analysis of 18q– using oligo-microarray comparative genomic hybridization (aCGH).  Am J Med Genet 149A:1431–1437, doi:10.1002/ajmg.a.32900.


    Linnankivi et al., (2006) 18q deletions: Clinical, molecular, and brain MRI findings of 14 individuals. AM J Med Genet 140A:331-339.


    Perry B, Sebold C, Hasi M, Heard P, Carter E, Gelfond J, Hale DE,  Cody JD. (2013) Sensorineural hearing loss in people with deletions of 18q.  Otol Neurotol. 2014 Jun;35(5):782-6. doi: 10.1097/MAO.0000000000000363. PubMed PMID: 24662633; PubMed Central PMCID: PMC4170734.


    Perry BP, Cody JD. Otologic characteristics of individuals with deletions of distal 18q. Laryngoscope. 2014 Nov;124(11):2606-9. doi: 10.1002/lary.24769.

    Soileau B, Hasi M, Sebold C, Hill A, O'Donnell L, Hale DE, Cody JD. (2014) Adults with Chromosome 18 Abnormalities. J Genet Couns. 24:663-674.


    van Trier DC, Feenstra I, Bot P, de Leeuw N, Draaisma JMTh (2013) Cardiac anomalies in individuals with the 18q deletion syndrome. Eur J Med Genet 56(8):426-431. doi: 10.1016/j.ejmg.2013.05.002