MED13L-Related Intellectual Disability Syndrome (MED13L Syndrome)

MED13L-related intellectual disability syndrome (MED13L syndrome) is a rare, genetic brain-development condition caused by changes in a single gene called MED13L. Children typically have global developmental delay (they learn skills like sitting, walking, and speaking later than peers), intellectual disability that ranges from mild to severe, low muscle tone (hypotonia), and characteristic facial features. Some children also have seizures, congenital heart defects, vision or hearing issues, feeding difficulties, and behavioral features such as autism-like traits or hyperactivity. The diagnosis is made by finding a disease-causing (pathogenic) change in one copy of the MED13L gene through modern genetic testing. There is no disease-specific curative medicine yet, so care focuses on early therapies, managing symptoms, and supporting families. NCBI  MED13L encodes a component of the Mediator complex, a master “on/off” switch that helps many other genes work properly during embryo and brain development. When one copy of MED13L is missing or not working (haploinsufficiency), development of the brain, face, limbs, and sometimes the heart is altered. Animal models and human studies support this mechanism. ScienceDirect+2Nature+2

MED13L-related intellectual disability syndrome is a genetic condition that mainly affects brain and body development. Most children have developmental delay, intellectual disability, and low muscle tone (hypotonia). Many also have speech delay, behavior or social differences (including features of autism), and a characteristic facial appearance. Some children have seizures and heart defects present from birth. The condition is usually caused by a change (variant) in one copy of the MED13L gene. This gene helps control how other genes turn on and off during development. When MED13L does not work well, many body systems are affected, especially the brain and heart. NCBI+2MedlinePlus+2

The condition is typically autosomal dominant. In most families, the MED13L change is de novo, which means it is new in the child and not found in either parent. Very rarely, a parent may carry the change in some cells (mosaicism) and have mild or no symptoms. MedlinePlus+1

Other names

Doctors and databases may use different names for the same condition. All of these refer to MED13L-related intellectual disability:

• MED13L syndrome

• MED13L haploinsufficiency syndrome

• Developmental delay–facial dysmorphism-cardiac defects syndrome due to MED13L deficiency

• Impaired intellectual development and distinctive facial features with or without cardiac defects (OMIM 616789)
  These labels all describe the same core picture: developmental delay/intellectual disability, distinctive facial traits, and sometimes heart defects. Orpha+2Global Genes+2

Types

There is no strict clinical staging, but experts often group MED13L syndrome by the kind of gene change and how it likely affects the protein:

1. Haploinsufficiency (loss-of-function): one MED13L copy is “broken” (deletions, nonsense/frameshift, certain splice changes). This is the most common and gives the classic syndrome. The MED13L Foundation+1

2. Missense variants (protein-changing): a single “letter” change alters the protein. Effects vary by location and can cause milder or, at times, atypical features. ScienceDirect+1

3. Intragenic deletions/duplications: a small chunk inside MED13L is missing or repeated. The MED13L Foundation

4. Chromosomal rearrangements affecting MED13L: rare translocations or complex changes disrupt the gene. The MED13L Foundation

These types all disturb the Mediator complex (a key gene-regulation machine in cells), which explains why many systems can be involved. Nature

Causes

“Cause” here means the specific genetic mechanism or risk context that leads to the syndrome:

1. De novo loss-of-function variant (new truncating change). This removes normal protein from one gene copy and is the single most common cause. NCBI+1

2. MED13L whole-gene deletion on chromosome 12q24.21. One copy is missing entirely. The MED13L Foundation

3. Frameshift variant (small insertion/deletion that shifts the code), usually inactivating. The MED13L Foundation

4. Nonsense variant (early “stop” signal), creating a shortened, non-working protein. The MED13L Foundation

5. Canonical splice-site variant that blocks proper RNA splicing, often acting like loss-of-function. The MED13L Foundation

6. Missense variant in critical domains (protein made but altered function), giving variable severity. ScienceDirect

7. Intragenic deletion (removes one or more exons), preventing normal protein assembly. The MED13L Foundation

8. Intragenic duplication (repeats exons), disturbing protein structure. The MED13L Foundation

9. Chromosomal translocation disrupting MED13L, rare but documented. The MED13L Foundation

10. Regulatory-region variant near MED13L that reduces gene expression (suspected in a few cases). Nature

11. Parental germline mosaicism, where a parent quietly carries the change in sperm/egg cells, raising recurrence risk. NCBI

12. Complex structural variants (e.g., inversions) involving the locus. The MED13L Foundation

13. MED13L gene conversion or microdeletion within repeat sequences, a mechanism seen in other loci and reported around MED13L in some series. The MED13L Foundation

14. Copy-number neutral deletions (gene-disrupting rearrangements) detected by genome sequencing. The MED13L Foundation

15. Deep-intronic splice variants missed by standard testing but found on RNA studies. (Rare; case reports.) The MED13L Foundation

16. Pathogenic variant arising post-zygotically (child mosaicism) causing milder or asymmetric features. (Rare; inferred from case series.) The MED13L Foundation

17. MED13L promoter methylation or expression disturbance secondary to nearby structural change. (Mechanistic reports.) Nature

18. Combined effect with other rare variants (“blended phenotype”) occasionally noted in exome studies. The MED13L Foundation

19. Uniparental disomy of chromosome segments including MED13L (theoretically possible, extremely rare; genome-wide testing rules this out). The MED13L Foundation

20. Pathway-level disruption of the CDK8-Mediator module (e.g., variants in related Mediator genes) can mimic the phenotype; distinguishing requires precise genetic testing. Nature

Common symptoms and signs

1. Global developmental delay: children reach milestones (sitting, walking, talking) later than peers. NCBI+1

2. Intellectual disability: learning and problem-solving are harder; severity ranges from mild to profound. NCBI

3. Low muscle tone (hypotonia): babies feel “floppy,” and motor skills can be slow to develop. NCBI

4. Speech and language delay: first words and sentences come late; some children are non-verbal. NCBI+1

5. Behavioral differences: traits of autism, hyperactivity, restlessness, or over-friendliness may appear. NCBI

6. Seizures (epilepsy): some children have recurrent seizures that need treatment. MedlinePlus

7. Congenital heart defects: these range from holes in the heart to complex outflow tract problems such as transposition of the great arteries. Nature+1

8. Distinctive facial features: examples include a bulbous nasal tip, full cheeks, and an open mouth posture. malacards.org

9. Feeding difficulties: poor suck or coordination in infancy; reflux is common. (Reported in series.) NCBI

10. Brain MRI differences in some children: thin or absent corpus callosum, delayed myelination, or ventriculomegaly. NCBI

11. Eye findings: strabismus (crossed eyes) or other vision issues. PMC

12. Hearing issues: a recent report highlights cochleo-vestibular involvement in some patients. PMC

13. Growth differences: some children have short stature or microcephaly; others have normal growth. (Series data.) The MED13L Foundation

14. Sleep problems: difficulties falling or staying asleep are reported by families. (Registry data.) Simons Searchlight

15. Coordination and gait challenges: ataxia or clumsiness can occur due to hypotonia and motor planning issues. malacards.org

Diagnostic tests

Doctors choose tests based on the child’s history and exam. Not every child needs every test. The goal is to confirm the genetic diagnosis, check for associated conditions, and guide care.

A) Physical examination

1. General pediatric and neurologic exam
   The doctor checks growth, head size, muscle tone, strength, reflexes, balance, and coordination. This maps the pattern of delay and looks for signs of seizures or neuromuscular issues that guide next tests. NCBI

2. Dysmorphology (genetics) exam
   A clinical geneticist looks for facial and body features typical of MED13L syndrome. Recognizing a constellation of findings raises suspicion and helps target genetic testing. Orpha

3. Cardiac exam (heart sounds, pulses, oxygen)
   A careful listen may pick up murmurs or extra sounds that suggest structural heart disease. This prompts heart imaging. Nature

4. Developmental assessment in clinic
   Observation of how the child plays, communicates, and moves helps gauge current skill levels and therapy needs. NCBI

5. Behavioral and sleep screening
   Short questionnaires screen for autism traits, ADHD-like symptoms, anxiety, or sleep problems so early supports can begin. NCBI+1

B) Manual/bedside tests

6. Standardized developmental testing (e.g., Bayley Scales, Vineland Adaptive Behavior Scales)
   These structured tasks measure cognition, language, motor, and daily living skills and are used to plan therapy and track progress. NCBI

7. Speech-language evaluation
   A speech therapist evaluates understanding, expression, articulation, and feeding/oral-motor skills, since speech and swallowing are commonly affected. NCBI

8. Physical and occupational therapy assessments
   Therapists test posture, tone, balance, fine motor control, and sensory processing to set an individualized program. NCBI

9. Vision assessment (cover-uncover, eye alignment checks)
   Simple clinic maneuvers can detect strabismus or tracking problems that need ophthalmology follow-up. PMC

10. Hearing screening (otoacoustic emissions/bedside audiology)
    Early screens suggest whether detailed audiology or imaging is needed, given reported cochleo-vestibular issues. PMC

C) Laboratory and pathological tests

11. Chromosomal microarray (CMA)
    Looks for missing or extra DNA pieces. It can detect MED13L deletions or duplications and other copy-number changes. The MED13L Foundation

12. Targeted MED13L sequencing or multigene neurodevelopmental panel
    Reads the MED13L “letters” to find small variants (missense, nonsense, frameshift, splice). Panels also check related genes with similar features. NCBI

13. Exome or genome sequencing
    Catches variants missed by panels and can reveal complex or deep-intronic changes; now widely used for undiagnosed developmental disorders. NCBI

14. Segregation (parental) testing
    Checks if the child’s variant is new (de novo) or inherited/mosaic, which changes recurrence risk counseling. MedlinePlus

15. Basic metabolic and thyroid labs (context-dependent)
    These do not diagnose MED13L syndrome but help rule out additional treatable causes of regression, poor growth, or hypotonia. NCBI

D) Electrodiagnostic tests

16. Electroencephalogram (EEG)
    Measures brain electrical activity to confirm and classify seizures, which informs medication choice. MedlinePlus

17. Electrocardiogram (ECG)
    Checks heart rhythm and conduction; valuable if a structural heart defect or symptoms are present. Nature

18. Brainstem auditory evoked responses (BAER/ABR)
    Objective hearing test useful in infants and nonverbal children, detecting auditory pathway issues early. PMC

E) Imaging tests

19. Echocardiogram (heart ultrasound)
    Looks for congenital heart problems, which can range from small holes to complex outflow tract defects. Nature

20. Brain MRI
    Evaluates structure and myelination; some children show thin or absent corpus callosum, ventriculomegaly, or delayed myelination. NCBI

21. Spine or hip radiographs (as indicated)
    Ordered if hypotonia, gait issues, or delayed walking raise concern for skeletal alignment problems. (Supportive practice.) NCBI

22. Ophthalmic imaging (as indicated)
    Ocular coherence tomography or retinal photos if vision concerns persist beyond basic exam. (Contextual.) PMC

23. Temporal bone or inner-ear MRI/CT (selected cases)
    Considered if detailed inner-ear anatomy is needed for hearing loss work-up. PMC

24. Abdominal or renal ultrasound (selected cases)
    Done if exam or history suggests other organ anomalies; not routine but sometimes helpful in syndromic evaluations. NCBI

25. Dental/craniofacial imaging (selected cases)
    If craniofacial concerns or suspected craniosynostosis are present (not universal). panelapp.genomicsengland.co.uk

Non-pharmacological treatments

There is no medicine that fixes the MED13L gene today. Care centers on early, intensive, family-centered therapies and supports. Below are 20 evidence-informed, practical interventions.

1. Early intervention programs. Enroll as soon as delay is suspected. These programs knit together PT/OT/SLT and family supports in the home or community, improving function and caregiver confidence. Pediatrics Publications+1

2. Individualized Education Program (IEP). School-based services tailor goals for speech, motor skills, behavior, and learning; regular reviews track progress and add AAC or therapies as needed. NCBI

3. Physical therapy (PT). PT builds head/trunk control, balance, and walking; it reduces contractures from hypotonia and encourages safe mobility and participation. NCBI

4. Occupational therapy (OT). OT targets hand use, self-care, and sensory regulation; home programs generalize skills to daily routines (dressing, feeding, play). NCBI

5. Speech-language therapy. Begin early—even before words—to build receptive language, gesture, and oral-motor skills; therapy intensity scales with need. kce.fgov.be

6. Augmentative & Alternative Communication (AAC). Picture exchange, communication books, or tablets give a “voice” when speech is limited; evidence supports AAC for young children with developmental disabilities. PubMed+1

7. Feeding therapy (SLP/OT). Trains safe swallowing, posture, textures, and caregiver techniques; coordinates with GI if reflux or aspiration are issues. ESPGHAN

8. Nutrition support. For poor growth or unsafe swallowing, a gastrostomy (G-tube) can provide reliable calories and decrease aspiration; families receive tube-care training. ESPGHAN+1

9. Behavioral interventions. Parent-mediated strategies and structured routines help address agitation, tantrums, or hyperactivity; approaches are tailored to the child’s profile. NCBI

10. Sleep hygiene program. Consistent schedules, light control, and screen limits are first-line for insomnia; consider melatonin only after behavioral strategies and clinician advice. HealthyChildren.org+1

11. Vision services. Early treatment of strabismus (glasses, patching, or surgery) prevents amblyopia and supports visual-motor development. NCBI

12. Hearing services. Hearing aids or other devices (when indicated) maximize language access; monitor hearing regularly. NCBI

13. Orthotics & mobility aids. Ankle–foot orthoses, gait trainers, or wheelchairs expand safe mobility and participation in school and community. NCBI

14. Care coordination & social work. Helps families access benefits, respite, equipment, transportation, and local disability services. NCBI

15. Genetic counseling. Explains inheritance (usually de novo), recurrence risks, and testing options in future pregnancies. NCBI

16. Cardiology follow-up (if heart defect). Echo surveillance and defect-specific plans (some small VSDs close; others need repair). www.heart.org+1

17. Orthopedics/spine clinic. Monitors scoliosis and foot/hand issues; intervenes early to preserve comfort and function. NCBI

18. Safety planning. Seizure first-aid education; aspiration precautions; home safety adaptations tailored to abilities. NCBI

19. Community & advocacy groups. Condition-specific groups (e.g., MED13L Foundation) connect families and promote research, natural-history studies, and trials readiness. The MED13L Foundation+1

20. Regular surveillance visits. Track development, behavior, seizures, nutrition, scoliosis, vision, hearing, and family needs at each visit using a structured checklist. NCBI

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Drug treatments

Medication choices depend on the child’s specific symptoms (for example, seizures, ADHD-like hyperactivity, severe sleep problems, reflux, or constipation). Always follow a specialist’s prescription and the official FDA label.

Anti-seizure medicines (examples from FDA labels):

1. Levetiracetam (Keppra). Widely used for pediatric epilepsy; available in liquid and tablet; dosing is weight-based and titrated by the neurologist; common adverse effects include irritability and somnolence. (Label shows pediatric indications and dosing details.) FDA Access Data+1

2. Valproate (valproic acid/divalproex). Broad-spectrum ASM; effective for generalized and focal seizures; avoid in pregnancy; monitor liver function and platelets; weight-based dosing. FDA Access Data+1

3. Other ASMs (per neurologist): clobazam, lamotrigine, topiramate, oxcarbazepine, lacosamide—selected based on seizure type/tolerability; labels provide dosing and safety specifics. (General principle that many ASMs can work in MED13L; none is disease-specific.) NCBI

Behavior/attention medications (when non-drug strategies are insufficient):

4. Methylphenidate for ADHD-like symptoms: improves attention and impulsivity in school-age children; monitor appetite, sleep, and blood pressure; follow label age indications and cautions. FDA Access Data+1

5. Non-stimulants (e.g., atomoxetine, guanfacine) may be considered if stimulants are poorly tolerated; follow FDA labels and specialist guidance. (Label-based class guidance; choice individualized.) NCBI

Sleep medicines (only after sleep hygiene and clinician review):

6. Melatonin (pharmaceutical-grade). Helps sleep-onset delay and circadian issues in neurodevelopmental disorders; use medical-grade products where possible due to supplement mislabeling; discuss dosing and timing with a clinician. American Academy of Neurology+2AASM+2

7. Tasimelteon oral suspension (Hetlioz LQ). FDA-approved for sleep disturbances in Smith-Magenis syndrome ages 3–15; occasionally considered by specialists for circadian rhythm issues—not specifically approved for MED13L. FDA Access Data+1

GI and other symptom medicines (as needed, label-guided):

8. Acid suppression (e.g., proton-pump inhibitors) for significant reflux to protect airway and growth, alongside feeding therapy. (Use per pediatric GI; label-specific.) ESPGHAN

9. Laxatives (e.g., polyethylene glycol) for constipation to support feeding and comfort—dosing per pediatric label and clinician plan. (General pediatric standard.) NCBI

10. Allergy/asthma medicines (if present) to improve sleep and feeding comfort—treat comorbidities per guidelines. (Comorbidity management principle.) NCBI

Important safety updates: U.S. FDA recently strengthened stimulant warnings about risks in very young children; off-label use under age 6 requires extra caution and specialist oversight. Reuters

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Dietary molecular supplements

Evidence for supplements in MED13L specifically is lacking. Some data from autism/ADHD literature suggest cautious, clinician-guided trials might help select symptoms. Always discuss with your pediatrician before starting supplements.

1. Omega-3 fatty acids (EPA/DHA). May modestly help attention or behavior in some neurodevelopmental conditions; product quality and dose vary; discuss risks/benefits. ScienceDirect+1

2. Vitamin D (if deficient). Correcting deficiency supports bone and muscle health; dose guided by labs and clinician. (General pediatric evidence.) NCBI

3. Iron (if iron-deficient). Iron deficiency can worsen sleep and attention; treat only if labs indicate deficiency. (General pediatric principle.) NCBI

4. Probiotics (selected strains). May help constipation; evidence variable; choose products with pediatric data and clinician input. (General supportive care.) NCBI

5. Multivitamin (age-appropriate). For restricted eaters to cover gaps—avoid megadoses. (General pediatric nutrition.) NCBI

6. Calcium (if low intake). Especially important if on tube feeds or limited dairy—dose per dietitian. (General pediatric nutrition.) ESPGHAN

7. Fiber supplements. Can relieve constipation together with fluids and diet changes. (GI supportive care.) ESPGHAN

8. Zinc (if deficient). Addressed based on labs to support growth/appetite. (General pediatric nutrition.) NCBI

9. Melatonin (as a hormone supplement). Treat like a medicine; use only with clinical guidance and pharmaceutical-grade sources because over-the-counter products are often mislabeled. AASM+1

10. Omega-3 + Vitamin D combinations. Studied in ASD/ADHD; any use should be individualized and monitored for benefits/side effects. Frontiers

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Immunity-booster / regenerative / stem-cell drugs

There are no approved immune boosters, regenerative medicines, or stem-cell drugs for MED13L syndrome. Using such products outside a regulated clinical trial can be risky and is not recommended. Research and natural-history work are underway to prepare for future trials (for example, the MED13L Foundation’s strategic plan and a natural history study). If you hear about “stem cell cures,” ask for peer-reviewed evidence and trial registration details. PMC+1

If considering any experimental therapy, discuss IRB-approved clinical trials with your genetics team and check ClinicalTrials.gov to verify legitimate studies. ClinicalTrials

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Surgeries

1. Cardiac defect repair (e.g., VSD). Some VSDs close spontaneously; larger defects or those causing heart failure/poor growth may need surgical or catheter-based closure. www.heart.org+1

2. Gastrostomy tube (G-tube). For chronically unsafe or insufficient oral intake to improve growth and reduce aspiration risk; caregivers are trained for home care. ESPGHAN

3. Strabismus surgery. If glasses/patching fail, surgery can align the eyes and prevent amblyopia. NCBI

4. Orthopedic procedures (e.g., tendon lengthening for contractures, scoliosis surgery in severe curves) to preserve comfort and function. NCBI

5. Cleft palate repair (if present) to improve feeding and speech resonance in children with palatal anomalies. NCBI

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Preventions

1. Early identification and referral to EI/therapies to prevent secondary delays. PMC

2. Vaccinations and infection prevention to reduce hospitalizations that derail progress. (General pediatric standard.) NCBI

3. Seizure safety plans at home/school to prevent injury. NCBI

4. Nutrition monitoring to prevent failure to thrive and micronutrient deficiencies. ESPGHAN

5. Constipation prevention (fluids, fiber, routines) to improve comfort and feeding. ESPGHAN

6. Sleep hygiene to prevent chronic insomnia and daytime behavior problems. HealthyChildren.org

7. Vision/hearing checks to prevent treatable sensory-related learning barriers. NCBI

8. Dental hygiene (especially with open-mouth posture) to prevent caries/gingivitis. (General pediatric principle.) NCBI

9. Cardiac follow-up for known defects to prevent heart failure or pulmonary hypertension. www.heart.org

10. Family support & respite to prevent caregiver burnout and maintain consistent therapies. NCBI

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When to see doctors urgently vs routinely

Urgent: seizures that last >5 minutes or cluster; new breathing trouble, cyanosis, or poor feeding in an infant with a known heart defect; signs of aspiration (coughing/choking with feeds, pneumonia); dehydration; severe constipation with vomiting; sudden regression in skills. NCBI

Prompt appointment: persistent sleep problems despite good hygiene; poor weight gain; worsening scoliosis or contractures; new hearing/vision concerns; behavior changes that limit learning or safety. NCBI

Routine: scheduled developmental, genetics, neurology, cardiology, ophthalmology, audiology, dentistry, PT/OT/SLT visits, plus standard childhood well-care. NCBI

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What to eat and what to avoid

What to eat: a balanced diet emphasizing fruits/vegetables, whole grains, adequate protein, calcium-rich foods, and sources of omega-3s (e.g., fish) if tolerated; for picky or unsafe eaters, work with a dietitian and feeding therapist; for tube-fed children, use pediatric formulas as directed. ESPGHAN

What to avoid: choking hazards if oral-motor skills are delayed; excessive added sugars and ultra-processed snacks that displace nutrients; unregulated “miracle” supplements or stem-cell products marketed as cures; any supplement without clinician review, especially melatonin gummies with mislabeled doses. Health

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Frequently asked questions

1. Is MED13L syndrome inherited? Usually not—most cases are de novo; rarely, a parent may be mosaic. Genetic counseling explains recurrence risks. NCBI

2. Can we predict severity from the variant? Not reliably; there is wide variability even with similar variants. NCBI

3. Is there a cure yet? No gene-specific therapy exists; treatment is supportive, therapy-focused, and symptom-based. NCBI

4. Are there clinical trials? Clinical-trial readiness and natural-history work are active; check reputable registries and foundation updates. PMC+1

5. When should we start therapies? As early as possible—early intervention improves outcomes. Pediatrics Publications

6. Will my child speak? Many children have limited or very late speech; AAC gives a voice and does not delay speech. PubMed

7. Do seizures change the plan? Yes—see neurology promptly; many anti-seizure medicines are effective; the choice depends on seizure type. NCBI

8. What about sleep? Start with sleep hygiene; consider clinician-guided melatonin or other therapies if needed. HealthyChildren.org

9. Are heart checks necessary? Yes, because a minority have congenital heart defects; cardiology will advise frequency. NCBI

10. Is hearing/vision important if development is delayed? Very—treatable sensory issues can greatly improve learning and behavior. NCBI

11. Do we need repeated MRIs? Only if clinically indicated; MRI mainly helps at diagnosis or if new neurologic concerns arise. NCBI

12. Should siblings be tested? Usually not unless symptoms or a familial variant exist; genetics will advise based on your family. NCBI

13. Can special diets cure MED13L? No—nutrition supports growth and energy but does not change the gene. Avoid unproven “cures.” NCBI

14. Where can we find trustworthy information and community? See GeneReviews and the MED13L Foundation for clinician-vetted material and family resources. NCBI+1

15. What genetic test should we ask for? Exome or genome sequencing is recommended early in the evaluation of GDD/ID. PubMed+1

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: November 11, 2025.