Congenital Myopathy–Cleft Palate–Malignant Hyperthermia Syndrome is a rare, inherited muscle disease starts at birth (congenital). Babies have weak muscles (a congenital myopathy), and many are born with a split in the roof of the mouth (cleft palate) and other face or bone features such as small eyelid openings (ptosis), short stature, club feet, and curved spine. A very important safety risk is a severe anesthesia reaction called malignant hyperthermia (MH), which can happen during surgery with certain gas anesthetics or with the muscle relaxant succinylcholine. The underlying cause in most families is harmful changes (pathogenic variants) in a gene called STAC3. This condition has also been called Native American myopathy, Bailey-Bloch congenital myopathy, and STAC3 disorder. MedlinePlus+3NCBI+3PubMed+3
Skeletal muscle cells need a clean “signal chain” to contract. A nerve impulse reaches the muscle and opens gates that release calcium from storage sacs inside the cell (the sarcoplasmic reticulum). In STAC3 disorder, changes in STAC3 disrupt that signal chain. Calcium release becomes abnormal, so muscles are weak from birth and fatigue easily. The same wiring problem also makes muscles over-react to certain anesthesia drugs, which can trigger malignant hyperthermia—an emergency with very high body temperature, fast heart rate, high carbon dioxide, rigid muscles, and dangerous blood changes. This is why every person with this syndrome (and their close relatives) must have clear anesthesia warnings in their medical records. NCBI+2NCBI+2
Other names
Native American myopathy (NAM) – first described in the Lumbee tribe in North Carolina. PubMed
Bailey-Bloch congenital myopathy – eponym used in later reports. MDPI
STAC3 disorder / STAC3 myopathy – preferred modern term linking the condition to the STAC3 gene. European Malignant Hyperthermia Group
Congenital myopathy with cleft palate and susceptibility to malignant hyperthermia – descriptive name used in early papers. PubMed+1
Types
Doctors usually talk about a spectrum rather than fixed subtypes:
Classic/Severe early-onset: profound neonatal hypotonia (very floppy baby), feeding problems, cleft palate, arthrogryposis (stiff joints), respiratory issues, and high MH risk. This was the pattern first seen in Lumbee families. PubMed
Moderate: congenital weakness with ptosis, myopathic face, short stature, spinal curvature; cleft palate may or may not be present; clear MH risk remains. Orpha
Milder, non-Native ancestries: overlapping features reported worldwide; still congenital myopathy with MH susceptibility, sometimes without obvious cleft palate. Nature+1
Causes
Think of “causes” here as underlying reasons and risk factors/mechanisms for this syndrome and for its key complications (especially malignant hyperthermia).
Biallelic STAC3 pathogenic variants (the main cause; autosomal recessive). NCBI
Founder variant (p.Trp284Ser) originally enriched in the Lumbee population. PubMed
Compound heterozygosity (two different harmful STAC3 changes, one on each copy). European Malignant Hyperthermia Group
Consanguinity or small founder communities, which raises the chance two carriers have a child together. PubMed
Disrupted excitation–contraction coupling in muscle due to STAC3 defects. NCBI
Secondary changes in calcium handling that predispose to MH crises during anesthesia. NCBI
Triggering anesthetic gases (halothane, sevoflurane, desflurane, isoflurane, enflurane). NCBI+1
Triggering muscle relaxant (succinylcholine). NCBI
Intercurrent infections or fever, which can worsen baseline weakness and breathing in infants (general congenital myopathy vulnerability). NCBI
Poor airway anatomy from cleft palate/micrognathia, complicating anesthesia and feeding. NCBI
Respiratory muscle weakness, raising risk for hypoventilation and chest infections. NCBI
Feeding difficulties from hypotonia/cleft palate, leading to poor growth. NCBI
Kyphoscoliosis progressing during growth and further reducing lung capacity. PubMed
Arthrogryposis causing fixed joint positions and motor delay. PubMed
Ptosis and facial weakness affecting eye opening and speech articulation. PubMed
Cardiorespiratory stress from MH episodes if triggers are used. NCBI
Unrecognized carrier status in parents (autosomal recessive inheritance risk of 25% per pregnancy). NCBI
Misdiagnosis as other congenital myopathies delaying MH precautions. NCBI
Lack of MH readiness (no dantrolene available) during procedures. NCBI
Limited awareness outside original populations, leading to missed STAC3 testing in diverse families. Nature
Symptoms and signs
Floppy baby (hypotonia) at birth—baby feels unusually soft and weak when held. PubMed
Delayed motor milestones—rolling, sitting, and walking happen later than usual. NCBI
Feeding trouble and poor weight gain, especially with cleft palate. NCBI
Cleft palate or high-arched palate affecting feeding and speech later on. PubMed
Ptosis (droopy eyelids) and a “myopathic facies” (reduced facial expression). PubMed
Short stature compared with peers. PubMed
Arthrogryposis (stiff joints) and talipes/clubfoot. PubMed
Kyphoscoliosis (curved spine) developing with growth. PubMed
Breathing weakness or recurrent chest infections due to weak respiratory muscles. NCBI
Nasal speech and articulation difficulty from cleft palate and facial weakness. NCBI
Fatigue with activity—muscles tire quickly. NCBI
Possible contractures (tight muscles/tendons) limiting range of motion. PubMed
Pain/cramps uncommon, but can occur, especially after illness or exertion. NCBI
Normal intelligence in most, with delays mostly motor/feeding rather than cognitive. PubMed
Life-threatening MH reaction during anesthesia if triggers are used (fever, rigid muscles, fast heart rate, high CO₂). Emergency. NCBI
How doctors diagnose it
A) Physical examination
General neuromuscular exam – checks muscle tone, strength, reflexes, and facial movement. Typical findings: generalized low tone and symmetric weakness, facial weakness, and droopy eyelids. Helps distinguish from brain causes of floppiness. NCBI
Craniofacial and palate exam – looks for cleft palate or high arch, micrognathia, and dental/airway features that impact feeding and anesthesia planning. PubMed
Orthopedic assessment – screens for arthrogryposis, club foot, hip issues, and spine curvature (kyphoscoliosis). Guides early therapy, splinting, or surgical timing. PubMed
Pulmonary evaluation at bedside – observes work of breathing, cough strength, and chest wall movement; early hints of respiratory muscle weakness prompt formal lung tests. NCBI
B) Manual/functional tests
Gross Motor Function measures (age-appropriate scales) – simple standardized tasks (head control, sitting, standing) to document delays and guide therapy goals over time. NCBI
Range-of-motion testing – goniometry of joints to track contractures from arthrogryposis and plan physical therapy or orthopedic care. PubMed
Airway assessment (Mallampati, mouth opening) – bedside checks predicting difficult intubation, especially with cleft palate/micrognathia, crucial to anesthesia safety planning. NCBI
C) Laboratory & pathological tests
Serum creatine kinase (CK) – often normal or only mildly raised in congenital myopathies; helps separate from muscular dystrophies where CK is high. NCBI
**Genetic testing—**targeted STAC3 sequencing or multigene myopathy/MH panels. A positive biallelic STAC3 finding confirms the diagnosis and triggers family counseling. NCBI+1
Carrier testing for parents/siblings – identifies relatives with one altered STAC3 copy; important for future pregnancies and MH risk awareness. NCBI
Muscle biopsy (when genetics is inconclusive) – light/electron microscopy may show congenital-myopathy patterns (e.g., fiber size variation); today biopsy is less often needed if genetics are diagnostic. NCBI
Basic metabolic panels during suspected MH – look for high potassium, acidosis, and rising creatine kinase; supports emergency treatment decisions. NCBI
Newborn screening review – not specific for STAC3 disorder, but helps exclude metabolic causes of hypotonia when results are normal. NCBI
D) Electrodiagnostic tests
Electromyography (EMG) – typically shows a “myopathic” pattern (small, brief motor unit potentials) without nerve damage, supporting a primary muscle problem. NCBI
Nerve conduction studies (NCS) – usually normal; help rule out peripheral neuropathies as a cause of weakness. NCBI
Caffeine–halothane contracture testing (CHCT/IVCT) in specialized centers – functional test on a fresh muscle sample to determine MH susceptibility; considered when genetic results are negative or unclear but MH risk is suspected. NCBI
E) Imaging & cardiorespiratory tests
Spine radiographs – detect and track kyphoscoliosis progression to time bracing or surgery and to anticipate restrictive lung disease. PubMed
Echocardiogram (as indicated) – baseline check because chronic muscle weakness and scoliosis can stress the heart over time; routine results are often normal but can guide peri-operative planning. NCBI
Pulmonary function tests (PFTs) – measure forced vital capacity and cough flows; key for monitoring respiratory muscle weakness and planning airway clearance strategies. NCBI
Sleep study (polysomnography) – evaluates nocturnal hypoventilation or sleep-disordered breathing that may occur with weak respiratory muscles and chest wall restriction. NCBI
Non-pharmacological treatments (therapies & supports)
Personalized physiotherapy program — Daily stretching and low-impact strengthening preserve joint motion and muscle function; regular movement helps muscle fibers work more efficiently and slows contractures. Purpose: maintain mobility; Mechanism: repeated, gentle loading improves muscle endurance and prevents stiffness. NCBI
Occupational therapy — Trains energy-saving habits and adaptive skills (dressing, writing, using tools). Purpose: independence; Mechanism: task-specific practice builds neural and motor patterns that bypass weakness. NCBI
Speech-language therapy — Addresses speech clarity and feeding/swallowing; safe-swallow strategies reduce choking and aspiration. Purpose: communication and nutrition; Mechanism: exercises and compensatory techniques improve oral-pharyngeal coordination. NCBI
Feeding support & nutrition planning — Texture modification, thickened liquids, and timed meals reduce fatigue and improve calorie intake. Purpose: growth and energy; Mechanism: lowers work of chewing/swallowing and prevents aspiration. NCBI
Respiratory therapy — Cough-assist devices, airway clearance, and nocturnal ventilation if needed. Purpose: protect lungs; Mechanism: improves ventilation and removes mucus when respiratory muscles are weak. NCBI
Orthotics and mobility aids — Ankle-foot orthoses, walkers, or wheelchairs; Purpose: safe movement; Mechanism: external support aligns joints and shares load with weak muscles. NCBI
Scoliosis surveillance & bracing — Regular spine checks; bracing may slow curves. Purpose: maintain sitting/breathing; Mechanism: mechanical support reduces progression in growing spines. NCBI
Cleft-palate team care (pre-/post-op) — Coordinated craniofacial, anesthesia, and airway planning; Purpose: safe palate repair and feeding; Mechanism: team planning optimizes timing and minimizes MH risk. NCBI
Sunrise-to-sunset energy budgeting — Structured day with rest breaks; Purpose: reduce fatigue; Mechanism: scheduled recovery prevents overuse of weak fibers. (Clinical best practice.)
Temperature caution education — Avoid overheating during illness or exercise; Purpose: safety; Mechanism: reduces physiologic stress that can exacerbate weakness. (Clinical best practice.)
Emergency plan & medical alert ID — Written MH emergency plan; Purpose: rapid response; Mechanism: speeds recognition and treatment (dantrolene access). mhaus.org
Vaccination & infection prevention — Routine immunizations and early treatment of chest infections; Purpose: avoid respiratory decline; Mechanism: prevents exacerbations in weak respiratory muscles. (Standard public-health practice.)
Sleep evaluation — Check for nocturnal hypoventilation; Purpose: brain and heart health; Mechanism: assisted ventilation stabilizes oxygen and CO₂ overnight. (Neuromuscular care norm.)
School & workplace accommodations — Extra time, elevator access, ergonomic tools; Purpose: inclusion; Mechanism: reduces physical strain while maintaining participation.
Psychological support — Counseling for child and family; Purpose: coping and resilience; Mechanism: skills training lowers anxiety and improves adherence.
Genetic counseling — Explains inheritance and carrier testing; Purpose: informed family planning; Mechanism: clarifies 25% recurrence risk in autosomal-recessive conditions. NCBI
Safe-anesthesia letter — A one-page note listing triggers to avoid and non-trigger alternatives; Purpose: pre-op safety; Mechanism: reduces accidental exposure. mhaus.org
Care coordination — A neuromuscular clinic that links PT/OT, pulmonology, orthopedics, craniofacial surgery, anesthesia; Purpose: consistent care; Mechanism: team reviews prevent gaps. NCBI
Telemedicine check-ins — Frequent short follow-ups; Purpose: earlier intervention; Mechanism: rapid adjustment of supports.
Community & registry participation — Connecting with MH resources and registries improves readiness and research participation. Purpose: empowerment; Mechanism: shared knowledge and access to MH hotline resources. AANA
Drug treatments
There is no medicine that fixes the underlying STAC3 gene problem today. Medicines are used for MH crisis management, for post-crisis care, and for supporting symptoms. The single most important life-saving drug is IV dantrolene. NCBI
1) Dantrolene (IV) — Ryanodex® (dantrolene sodium)
What it’s for: First-line emergency treatment of malignant hyperthermia during anesthesia.
Class & mechanism: Skeletal muscle relaxant that lowers calcium release from the sarcoplasmic reticulum (via ryanodine receptors), reversing the hypermetabolic state.
Dosage & timing (typical in labels): Initial 2.5 mg/kg IV, repeat as needed until signs subside; continue as indicated.
Purpose: Stop the MH crisis.
Key cautions/side effects: Weakness, potential interactions; avoid combining with calcium channel blockers during MH treatment because of risk of cardiovascular collapse and hyperkalemia. FDA Access Data+1
2) Dantrolene (IV) — Dantrium® Intravenous
Indication: Treatment and prevention/attenuation of recurrent MH signs peri- and post-operatively.
Label highlights: Can be given pre-op in patients judged MH-susceptible; post-crisis, can help prevent recurrence while transitioning to oral therapy.
Effects: Similar therapeutic action as above; formulation differs from Ryanodex. FDA Access Data+1
3) Dantrolene (oral) — Dantrium® capsules
Use: After an MH crisis, oral Dantrium 4–8 mg/kg/day in divided doses for 1–3 days is commonly recommended in labeling to prevent recurrence.
Cautions: Contraindicated in active liver disease; monitor for hepatic toxicity and CNS effects. FDA Access Data+1
4) Avoid succinylcholine (depolarizing neuromuscular blocker)
Why: Triggers MH and can cause life-threatening hyperkalemia in susceptible or myopathic patients.
FDA labels explicitly warn about MH risk and advise temperature/ETCO₂ monitoring; dantrolene is recommended if MH occurs. FDA Access Data+2FDA Access Data+2
5) Avoid volatile anesthetic gases (e.g., desflurane)
Why: Labeled contraindication in patients with known or suspected MH susceptibility; discontinue all triggers and give IV dantrolene if MH is suspected. FDA Access Data+2FDA Access Data+2
6) Non-triggering anesthetic plan (safe agents)
Approach: Use total intravenous anesthesia (e.g., propofol-based) and non-depolarizing neuromuscular blockers as needed; these are considered safe for MH-susceptible patients per specialty guidance. (Drug choices are individualized by anesthesia team.) mhaus.org
Note: Beyond dantrolene and trigger avoidance, no other FDA-approved drugs specifically treat STAC3 disorder itself. Supportive meds (e.g., reflux control, constipation regimens, vitamin D for bone health) may be used for associated problems, but they do not change the muscle disease.
Dietary molecular supplements
There’s limited, mixed evidence for supplements in congenital myopathies; use only under clinician guidance to avoid interactions and false expectations. Possibilities sometimes discussed in neuromuscular practice include: creatine monohydrate, L-carnitine, Coenzyme Q10, vitamin D, omega-3 fatty acids, magnesium (if deficient), riboflavin, thiamine, whey protein, and a balanced multivitamin. These aim to support energy metabolism, correct deficiencies, and reduce fatigue, but none are proven to modify STAC3 disease biology. (Discuss with your neuromuscular clinician; monitor labs and side-effects.)
Immunity booster / regenerative / stem-cell drugs
There are no approved regenerative or stem-cell drugs for STAC3 disorder or for preventing MH. Stem-cell infusions or “immune boosters” marketed online are unproven and may be harmful. If you see clinical trials for gene or cell therapy in congenital myopathies, those are experimental and have strict eligibility rules; talk to your specialist about reputable trials. (This section is intentionally cautionary to keep patients safe.)
Surgeries (procedures & why they’re done)
Palatoplasty (cleft-palate repair) — Restores separation between mouth and nose; improves feeding and speech. Careful MH-safe anesthetic planning is required. NCBI
Ptosis repair — Lifts droopy eyelids to protect vision and improve field of view; timing individualized. NCBI
Scoliosis correction (spinal fusion when indicated) — Straightens and stabilizes the spine to improve sitting balance and lung function. MH precautions apply. NCBI
Gastrostomy tube placement — Provides reliable nutrition/hydration if swallowing is unsafe or exhausting; reduces aspiration risk. NCBI
Tracheostomy (selected cases) — Secures the airway and allows long-term ventilation if respiratory muscles are very weak. NCBI
Prevention tips
Carry an MH medical alert and a written anesthesia plan. mhaus.org
Tell every surgeon/anesthetist about MH risk before any procedure. mhaus.org
Avoid known triggers (volatile gases, succinylcholine) and insist on a non-triggering technique. mhaus.org
Ensure dantrolene availability wherever anesthesia is given. mhaus.org
Keep vaccinations up to date and practice good hand hygiene to prevent chest infections.
Use pacing and heat-avoidance during exercise/illness to limit over-exertion.
Home safety: fall-proof spaces; use appropriate mobility aids.
Nutrition: maintain healthy weight to reduce strain on weak muscles.
Genetic counseling for family planning and to identify carriers. NCBI
Join MH/rare-disease networks for updated guidance and emergency resources. AANA
When to see a doctor (or go to the ED)
Immediately if after anesthesia you notice: fever, rigid or painful muscles, fast breathing, dark urine, confusion, or a very fast heartbeat—this can be MH and is an emergency. FDA Access Data
Promptly if you see more choking, weight loss, pneumonia, sleepiness in daytime, morning headaches (possible nocturnal hypoventilation), or worsening spine curve.
Regularly for neuromuscular clinic follow-ups to update therapy and equipment.
What to eat and what to avoid
Emphasize: balanced meals rich in protein (for muscle repair), fruits/vegetables (micronutrients), whole grains (energy), healthy fats (omega-3s), and adequate hydration. Small, frequent meals can reduce fatigue with chewing/swallowing.
Correct deficiencies: vitamin D, iron, B-vitamins, and magnesium if low (checked by labs).
Avoid/limit: very tough foods if chewing is weak; alcohol excess (falls, sedation); fad “mega-dose” supplements not prescribed; dehydration and overheating. (These steps support health but do not change the gene defect.)
FAQs
1) Is this curable? Not yet. Current care is supportive and safety-focused; research is ongoing. NCBI
2) Is every anesthetic dangerous? No. Only volatile gases and succinylcholine are proven MH triggers; non-triggering techniques are safe when used properly. mhaus.org
3) What drug treats an MH crisis? IV dantrolene plus cooling and supportive care. FDA Access Data+1
4) Can I take oral dantrolene after a crisis? Labels describe short post-crisis courses to prevent recurrence; your team decides based on your case. FDA Access Data+1
5) Are there types of STAC3 disorder? Doctors describe a spectrum of severity, not formal subtypes. NCBI
6) Will physiotherapy help? Yes—helps mobility and slows stiffness, though it can’t change the gene. NCBI
7) Is cleft-palate repair safe? Yes, with MH-safe anesthesia and a craniofacial team; timing is individualized. NCBI
8) Which medicines must be avoided? Succinylcholine and volatile anesthetics; your anesthesia team will choose safe alternatives. FDA Access Data+1
9) Should family members be tested? Genetic counseling and testing help clarify carrier status and plan safely. NCBI
10) Is routine surgery (e.g., dental) possible? Yes—with MH precautions and dantrolene availability. mhaus.org
11) Do supplements cure this? No. Some may support general health; discuss risks/benefits first.
12) Can infections make breathing worse? Yes; prevention and early treatment are important in weak respiratory muscles.
13) Are vaccines safe? Yes—follow your country’s schedule unless your clinician says otherwise.
14) Can I exercise? Gentle, regular activity with rest breaks is encouraged; avoid overheating and exhaustion.
15) Where can I learn more about MH? See MHAUS resources and the MH hotline for clinicians. AANA
Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.
The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: October 16, 2025.
