Handbook of Genetic Counseling/1p36 Deletion Syndrome-1

1p36 Deletion Syndrome

Introduction

• Introduce myself and acknowledge that I will be involved in their visit today.
• Let them know that Counselor1 and Dr. Doktour will also be visiting with them today.
• Small talk while walking to the room.
• "What are your main concerns or questions that you would like addressed today?"

Interim History

• Explain that all of their concerns will be addressed later in the session, but that I would like to update the medical and developmental history from her last visit in February.
• Who is her pediatrician? Any other physicians?
• Any serious illnesses, hospitalizations or surgeries since February?
• Current Medications?
• Immunizations up to date?

Review of Systems

• Any diet or feeding concerns?
• Any changes in skin pigmentation or birth marks?
• Any heart concerns? (cardiologist found none)
• Any bladder problems?
• Any concerns about her hearing? Ear infections? PE tubes?
• Any concerns with her behavior or sleep?
• Any bowel problems? Constipation?
• Any allergies?
• Any concerns about vision or eyes?
• Any concerns about seizures? Starring spells or repetitive behaviors?
• Any other medical concerns (difficulty breathing)

Developmental Assessment

• Language
  • How many words does she have in her vocabulary?
  • Is she learning to sign? How many signs does she know?
  • Does she combine words into two word sentences?
  • Does she follow one or two step commands?
  • Can she point to any body parts?
  • How well is she able to indicate her wants?
• Gross Motor
  • Is she standing independently?
  • Is she cruising?
  • Is she walking? Up stairs?
• Visual Motor
  • How well does she hold and manipulate a crayon?
  • Drink from a cup?
  • Uses a spoon to feed? Started using a fork?
  • Can she help undress or dress herself?
• Social
  • Imitates housework?
  • Behavior? (Rocking)

• How do you feel her development compares with other children?
• Do you feel she is making progress?

Early Intervention

• Ask about OT, PT and speech therapy.
• How often?
• Where is she receiving services?
• What are they working on and what are the goals?
• Is insurance covering these costs?
• How do you think she is progressing?

Psychosocial Assessment

• Are all your other children living at home?
• Things must be really hectic attending all her appointments and services on top of having ____ other children at home. How does it all work out?
• Do you have help from other family members or others?
• Do you have contact with any other families with 1p36 deletion syndrome?

Etiology of 1p36 deletion syndrome (monosomy 1p36)

• Caused by deletion of the most distal band of the short arm of chromosome1.
• Most clinical manifestations are probably caused by the absence of one copy of a dose-sensitive gene and it is not possible to replace missing genes from chromosomes at this time.
• Prevalence of this deletion is estimated to be 1 in 10,000 to as high as 1 in 5,000 (making it the most common terminal deletion)
• Most cases result from sporadic deletions and are not inherited
• 1p36 deletion syndrome is usually diagnosed through recognition of the symptoms and characteristics as well as lab testing. This is done using high resolution chromosome analysis, or FISH with a chromosome 1-specific subtelomeric probe. The deletion often doesn't show up clearly with standard cytogenetic banding techniques. (In one group studied, about half were missed with chromosome analysis)
• Patients with a 1p36 deletion have different sized pieces of the chromosome missing and may result in phenotype variability
• Severity of associated disorders varies, but the physical features are very similar
• Degree of MR and ability to acquire complex speech is somewhat dependent on deletion size
• Most deletions affect the chromosome inherited from the mother (68%), but there doesn't seem to be differences in the clinical manifestations based on whether the deletion is on the paternal or maternal chromosome.
• Those with paternally derived deletions tend to have larger deletions than those with maternally derived deletions
• Mechanism causing chromosome breakage is unknown

Characteristics

• Children with 1p36 deletion syndrome are all unique individuals, but do have some common characteristics.
• Distinct facial features including: small and pointed chin, flat nasal bridge, low-set ears, ear asymmetry, thickened ear helices, small head, deep-set eyes, large anterior fontanel, clinodactyly and/or short fifth finger
• Most patients have mental retardation
• Most patients have delayed growth and/or difficulty gaining weight. Some have difficulty with sucking and swallowing while others may not grow well even though they eat well. Some older children may become obese.
• Most young children with 1p36 deletion syndrome have delayed development.
• They sit up, walk and talk later than typical children.
• Speech is severely affected with many patients learning only a few words
• Other medical problems: hypotony (which may explain delayed motor skills), hearing loss, seizures, eye/vision problems, hypothyroidism, increased risk for neuroblastoma, heart defects (which have included cardiomyopathy, ductus arteriosus, tetralogy of Fallot, VSD), and orofacial clefting abnormalities,

Recurrence Risk for next pregnancy

• The majority of patients with 1p36 deletion syndrome are isolated cases resulting from a de novo deletion. There have been reports of patients with 1p36 deletion syndrome whose parents have a balanced translocation.
• Parents should be tested for chromosomal rearrangements because about 6% of parents with an affected child have a balanced translocation
• Translocation increases the chances of having another child with a 1p36 deletion.
  • If no translocation is found the chances of having another child with a 1p36 deletion are very small

Prenatal Diagnosis

• In 1999 a case was reported in which a 1p36 deletion in a fetus was detected when an amniocentesis was performed due to detection of multiple malformations on ultrasound
• Another case was picked up prenatally because of the presence of elevated maternal serum alpha-fetoprotein (no abnormal sign seen on ultrasound).
• Another was diagnosed prenatally because the mother was known to have a balanced translocation between the short arms of chromosome 1 and 20 that was picked up after their first child had inherited an unbalanced product. (no abnormal sign seen on ultrasound)

Medical Treatment

• Seizures can usually be controlled with medication
• Medical interventions and feeding therapy may be needed to manage feeding issues
• Early Intervention for developmental delay
• Surgery may be necessary to correct heart defects, cleft lip, cleft palate if present
• A urine screen for neuroblastoma should be performed every 6 months
• Physical examinations should involve palpating the abdomen for lumps which might be neuroblastomas
• There are no clear indications on whether they should continue to be followed by a cardiologist or whether the cardiomyopathy is limited to a congenital form.

Psychosocial Issues

• Initially parents may experience denial about how severe the developmental delay and mental retardation will be
• Blaming of self or partner may occur
• Stress of having a child with developmental delays and mental retardation
• Stress associated with having a child with serious medical problems especially if they have heart malformations or seizures
• Fear that the child might develop a neuroblastoma or seizures
• Time commitment involved with early intervention services (OT, PT, speech therapy)

Patient Resources

• Chromosome Deletion Outreach [1]
• MUMS [2]

References

• Shaffer, L.G. and Heilstedt, H.A. Terminal Deletion of 1p36. The Lancet Supplement December 2001; 358:89.
• Faivre, L. et al. (1999) Prenatal Detection of a 1p36 Deletion in a Fetus with Multiple Malformations and a Review of the Literature. Prenatal Diagnosis. 19:49-53
• Heilstedt, H.A. et al. (2001) Loss of the Potassium Channel B-subunit gene, KCNAB2, Is Associated with Epilepsy in Patients with 1p36 Deletion Syndrome. Epilepsia. 42(9):1103-1111.
• 1p36 patient literature by Counselor1 that is currently in the process of being completed

Notes

The information for this outline was last updated in 2002.