Handbook of Genetic Counseling/Hypotonia - Developmental Delay

Hypotonia - Developmental Delay

Contracting

• Introductions, acknowledge prior contact
• Assess main concerns of patient
• Why are they visiting Genetics today?
  • What do they hope to gain from the session?
    • explore desire to have a diagnosis
      • mother previously mentioned that they had come to terms with not having a diagnosis
• Overview of today's session
  • Restate patient's concerns
  • Medical history, family history, physical exam, genetics, recurrence risk, testing options and limitations

Pediatric Intake

• Family History
  • any relatives with hypotonia? developmental delay or learning disabilities? MR? -- no to all
  • history of infant deaths or miscarriages? birth defects? -- no
  • diabetes? cancer? thyroid prolems? heart problems? respiratory problems? genetic conditions? -- no to all
  • consanguinity? -- no

Differential Diagnosis

• Canavan disease
  • autosomal recessive
  • characterized by developmental delays by age 3-5 months, severe hypotonia involving "head lag", and inability to sit, walk, or speak
  • hypotonia eventually changes to spasticity and help with feeding is necessary
  • macrocephaly
  • Testing
    • urine analysis for concentration of N-acetylaspartic acid (NAA)
      • increased in affected patients
    • blood analysis for levels of aspartoacylase enzymatic activity
      • often unmeasurable in affected patients

Myotonic Dystrophy

• • autosomal dominant
  • incidence of 1/20,000
  • suspected in infants with hypotonia, facial muscle weakness, generalized weakness, club foot, and respiratory insufficiency or failure
  • Mild -- characterized by cataract and mild myotonia
  • Classic -- characterized by muscle weakness and wasting, cataracts, myotonia, cardiac conduction abnormalities
  • Congenital -- hypotonia, severe generalized weakness at birth, often have respiratory problems and early death, MR common
  • Testing
    • DNA analysis is 100% sensitive
      • detects an expansion of the CTG trinucleotide repeat in the DMPK gene (19q13)
    • > 37 repeats is abnormal
    • > 50 repeats are symptomatic
    • > 1000 repeats often seen in congenital type
• Cerebellar Ataxia
  • most types have onset in adulthood
  • Spinocerebellar Ataxia 7 -- failure to thrive and loss of motor milestones, loss of vision
  • Spinocerebellar Ataxia 8 -- common initial symptoms are scanning dysarthria with a characteristic drawn-out slowness of speech and gait instability, hyperactive tendon reflexes
    • onset can be as early as one year old
    • Testing -- CTA/CTG expansion in the SCA8 gene (13q21) can be detected via DNA analysis
• Aicardi syndrome
  • X-linked dominant inheritance
  • characterized by the partial or complete absence of the corpus callosum (the structure that links the 2 hemispheres of the brain), infantile spasms, mental retardation, and an ocular abnormality called lacunae (lesions) of the retina of the eyes
  • may be associated with other brain defects such as microcephaly or porencephalic cysts (cerebrospinal fluid-filled cavities or gaps in the brain)
  • onset generally begins between the ages of 3 and 5 months
• Myasthenia gravis (familial infantile)
  • autosomal recessive
  • characterized by respiratory and feeding difficulties in an infant
  • absence or weakness of the ocular muscles is also characteristic
• Familial Dysautonomia
  • characteristics include lack of tearing, emotional lability, paroxysmal hypertension, increased sweating, cold hands and feet, corneal anesthesia, erythematous blotching of the skin, and drooling
  • the absence of the fungiform papillae of the tongue is also characteristic
  • scoliosis is often severe and neuropathic joints of the Charcot type may develop
  • Ashkenazi-Jewish heritage is common

Previous Testing

• chromosomal testing done previously -- results normal

Psychosocial Issues

• • How important is a diagnosis to you?
  • If the visit to Genetics does not result in a diagnosis, what will this mean to you?
  • Are you worried about your child having a "label"?
• Financial concerns
• Support Network
  • do attend meeting of "Mother of Special Children" each month
  • support from family? friends? church?
• Educational concerns

Support Groups and Resources

• Mothers of Special Children

www.mothersofspecialchildren.com

meet the second Monday of each month at 7:30

Hyde Park Bethlehem United Church

Hyde Park and Madison Road

• Ohio Coalition for the Education of Children with Disabilities

www.ocecd.org

Director: Margaret Burley

Co-Director: Lee Ann Derugen

Executive Office

165 West Center Street, Suite 302

Marion, OH 43302-3741

Phone (740) 382-5452 or (800) 374-2806 (in Ohio)

Fax (740) 383-6421

E-mail: ocecd@gte.net

• March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue

White Plains, NY 10605

email: resourcecenter@modimes.org

internet: http://www.modimes.org

Tel: 914-428-7100 888-MODIMES (663-4637)

Fax: 914-428-8203

References

• www.geneclinics.org (Canavan syndrome, Myotonic Dystrophy, Cerebellar Ataxia)
• Smith's Recognizable Patterns of Human Malformation
• OMIM #304050 (Aicardi syndrome), #254210 (Myasthenia gravis), #223900 (Familial Dysautonomia)
• National Institute of Neurological Disorders and Stroke
  • Aicardi syndrome information page

http://www.ninds.nih.gov/health_and_medical/disorders/aicardi.htm

Notes

The information in this outline was last updated in 2002.