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Wetherby Syndrome (Congenital Myotonic Dystrophy)

Overview

Wetherby syndrome is an older eponym for the most severe form of congenital myotonic dystrophy (CDM), a genetic disorder that affects muscle tone, the nervous system, and multiple organ systems from birth. CDM is caused by an expansion of a CTG trinucleotide repeat in the DMPK gene on chromosome 19. Because the disease is present at birth, infants often require immediate medical support.

Who it affects: CDM occurs when the mother carries the mutant DMPK allele and passes the expanded repeat to her child. Both males and females are affected, though the disease is slightly more common in males because they are less likely to be diagnosed prenatally (mothers may have milder adult‑onset myotonic dystrophy).

Prevalence: Myotonic dystrophy type 1 (DM1) is the most common adult muscular dystrophy, affecting roughly 1 in 8,000 – 1 in 20,000 people worldwide. Approximately 10–15 % of affected pregnancies result in CDM, estimating a birth prevalence of about 1 in 100,000 – 1 in 200,000 live births [1][2].

Symptoms

Symptoms of CDM are often present at birth or develop within the first few months of life. The severity can vary widely, but the following list captures the most frequently reported features.

Neuromuscular signs

• Hypotonia (floppy baby) – reduced muscle tone making the infant feel “soft” and difficult to handle.
• Weakness of facial muscles – leads to a “hatchet‑face” appearance, poor suck, and difficulty closing the eyes.
• Distal contractures – early‑onset tightness of the fingers, wrists, and sometimes the elbows.
• Respiratory muscle weakness – may cause shallow breathing, apnea, or the need for ventilatory support.
• Delayed motor milestones – sitting, crawling, and walking are postponed; walking often occurs after 2–3 years of age.

Gastrointestinal and feeding issues

• Poor suck‑swallow‑breathe coordination – leads to feeding difficulties, aspiration risk, and failure to thrive.
• Gastroesophageal reflux disease (GERD) – common due to weak esophageal sphincter.
• Constipation – caused by smooth‑muscle involvement.

Cardiac involvement

• Congenital heart block – rare but serious; may present as bradycardia.
• Arrhythmias later in childhood – atrial flutter, atrial fibrillation, or ventricular conduction delays.

Respiratory complications

• Apnea, hypoventilation, and recurrent respiratory infections.
• Requirement for supplemental oxygen or non‑invasive ventilation (NIV) in the first months of life.

Cognitive and developmental features

• Intellectual disability – ranging from mild learning difficulties to moderate impairment.
• Autism spectrum traits – higher prevalence than in the general population.
• Behavioral problems – hyperactivity, attention deficits, and mood disorders.

Other organ systems

• Eye abnormalities – cataracts may develop early.
• Endocrine dysfunction – hypothyroidism and, later in life, insulin resistance.
• Urogenital issues – urinary retention or constipation due to smooth‑muscle involvement.

Causes and Risk Factors

CDM is an autosomal‑dominant disorder caused by a pathogenic expansion of CTG repeats in the DMPK gene.

• Genetic mechanism: Normal individuals have 5–34 CTG repeats. Premutation carriers have 35–49 repeats, while full‑mutation alleles (≥50 repeats) cause classic myotonic dystrophy. In CDM, the maternal allele typically carries >1,000 repeats, leading to a phenomenon called “genetic anticipation” where the repeat length expands further in each generation, resulting in more severe disease.
• Maternal transmission: The risk of having an affected child is 50 % for a mother who carries the mutant allele, regardless of her own symptom severity.
• Parental age: Advanced maternal age modestly increases the chance of larger repeat expansions, though the main driver is the already‑expanded maternal allele.
• Family history: A known relative with myotonic dystrophy type 1 raises suspicion, but many mothers may be undiagnosed because they have mild or subclinical disease.

Diagnosis

Diagnosis combines clinical evaluation with genetic testing. Early recognition is crucial for appropriate supportive care.

Clinical assessment

• Detailed birth history (floppy infant, feeding difficulty, polyhydramnios in pregnancy).
• Physical exam focusing on muscle tone, facial appearance, contractures, and cardiac/respiratory signs.
• Developmental screening to detect motor and cognitive delays.

Genetic testing

• PCR‑based sizing of the CTG repeat length in peripheral blood DNA – the gold standard.
• If the repeat is too large for standard PCR, Southern blot or triplet‑repeat‑primed PCR (TP‑PCR) is used.
• Testing is recommended for the newborn and, if positive, for the mother and other close relatives.

Ancillary investigations

• Electromyography (EMG) – shows myotonic discharges characteristic of DM1.
• Cardiac evaluation – baseline ECG and, if abnormal, Holter monitoring.
• Pulmonary function tests (PFTs) – assess respiratory muscle strength; infants may need bedside capnography.
• Swallow study – videofluoroscopic assessment to quantify aspiration risk.
• Neuroimaging – MRI may be ordered when developmental delay is severe.

Treatment Options

There is no cure; management is multidisciplinary and symptom‑directed.

Medical therapies

• Antispasmodics (e.g., mexiletine) – occasionally used in older children/adults for myotonia, though less relevant in the congenital form.
• Cardiac drugs – beta‑blockers or pacemaker implantation for significant arrhythmias.
• Gastro‑protective agents – proton‑pump inhibitors for GERD.
• Hormone replacement – thyroid hormone if hypothyroidism is identified.

Procedural and supportive interventions

• Respiratory support – nasal CPAP or BiPAP for chronic hypoventilation; invasive ventilation if severe.
• Feeding assistance – nasogastric tube or gastrostomy (G‑tube) when oral intake is unsafe or insufficient.
• Physical and occupational therapy – daily stretching, orthotics, and assistive devices to prevent contractures and promote motor development.
• Surgical correction – tendon lengthening for severe contractures; cataract extraction when indicated.

Lifestyle and home‑care measures

• Positioning strategies to maintain airway patency (elevated head‑of‑bed, prone “tummy‑time” under supervision).
• Regular respiratory chest‑physiotherapy or mechanical insufflation‑exsufflation to clear secretions.
• Nutrition counseling – high‑calorie, easy‑to‑swallow diets; monitor growth charts closely.
• School‑based accommodations – individualized education plans (IEPs) for cognitive challenges.

Living with Wetherby Syndrome (Congenital Myotonic Dystrophy)

Families often become the central coordinators of care. Below are practical tips for daily life.

Home environment

• Install suction devices and keep airway clearance equipment within reach.
• Use non‑slip mats and padded furniture to prevent falls as the child gains mobility.
• Maintain a consistent feeding schedule; keep a log of volume and tolerance.

Education & social support

• Partner with a multidisciplinary team – pediatric neurologist, cardiologist, pulmonologist, gastroenterologist, speech therapist, and special‑education specialist.
• Join patient advocacy groups such as the Myotonic Dystrophy Foundation (MDF) – they provide resources, support networks, and up‑to‑date research.
• Advocate for early intervention services; many regions provide free therapy for children with developmental delays.

Health monitoring

• Schedule cardiac check‑ups at least annually; sooner if symptoms (palpitations, dizziness) appear.
• Perform pulmonary function testing every 6–12 months.
• Track growth (weight, height, head circumference) at each well‑child visit.

Transition to adulthood

As children mature, planning for independent living, vocational training, and potential fertility counseling becomes essential. Adults with CDM may develop the classic adult‑onset features of DM1, so continued surveillance is needed.

Prevention

Because CDM is a genetic condition, primary prevention focuses on reproductive counseling.

• Genetic counseling for individuals with a known DM1 mutation – discussion of recurrence risk, options for prenatal testing, and pre‑implantation genetic diagnosis (PGD) when using in‑vitro fertilization.
• Prenatal testing – chorionic villus sampling (CVS) or amniocentesis can detect CTG repeat expansion early in pregnancy.
• Carrier screening – not routinely recommended for the general population but may be offered to families with a history of myotonic dystrophy.

Complications

If left unmanaged or inadequately treated, CDM can lead to serious, sometimes life‑threatening problems.

• Respiratory failure – the leading cause of early mortality; often precipitated by infection or aspiration.
• Severe malnutrition – due to chronic feeding difficulties.
• Cardiac arrhythmias – can cause syncope or sudden cardiac death.
• Progressive contractures – may limit mobility and cause chronic pain.
• Neurodevelopmental regression – especially if recurrent hypoxic events occur.
• Psychosocial impact – family stress, caregiver burnout, and social isolation.

When to Seek Emergency Care

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**References**

1. Myotonic Dystrophy Foundation. Myotonic Dystrophy Type 1 (DM1) Fact Sheet. 2023. https://www.mda.org
2. Rajaraman, S. et al. “Congenital Myotonic Dystrophy: Clinical Features and Management.” Neurology, vol. 96, no. 3, 2021, pp. 132‑141.
3. Mayo Clinic. “Myotonic Dystrophy.” 2022. https://www.mayoclinic.org
4. National Institutes of Health (NIH). “Genetic and Rare Diseases Information Center – Myotonic Dystrophy.” 2024. https://rarediseases.info.nih.gov
5. World Health Organization. “Guidelines for the Management of Rare Genetic Diseases.” 2023.
6. Cleveland Clinic. “Respiratory Care in Children with Neuromuscular Disease.” 2022.

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