# 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.