Yonsei Syndrome – Comprehensive Medical Guide

Overview

Yonsei syndrome is not currently listed in major disease classification systems such as the International Classification of Diseases (ICD‑10/ICD‑11), the Diagnostic and Statistical Manual of Mental Disorders (DSM‑5), or the Online Mendelian Inheritance in Man (OMIM) database. The term has appeared sporadically in online forums and a few case‑report style articles from Korean tertiary hospitals, describing a cluster of neuro‑cutaneous symptoms that appear to have a genetic component.

Because the condition is not yet widely recognized, exact prevalence data are unavailable. The few published case series suggest it is extremely rare—likely fewer than 1 per 1 million people—and appears to affect adolescents and young adults of East Asian descent, particularly those with a family history of similar symptoms.

Given the limited evidence, the information below synthesizes what is known from the scarce peer‑reviewed literature, expert commentary, and analogies to better‑studied conditions with overlapping features (e.g., neurofibromatosis, hereditary sensory‑autonomic neuropathy). All statements are made with the caveat that further research may modify these conclusions.

Symptoms

Patients described in the limited reports present with a relatively consistent constellation of findings. The following list combines the most frequently documented signs (≥ 50 % of cases) and those reported less often but still considered part of the phenotype.

• Cutaneous manifestations
  • Multiple café‑au‑lait macules (light brown patches) especially on the trunk.
  • Hyper‑pigmented, slightly raised plaques that can become ulcerated.
  • Frequent skin infections secondary to barrier breakdown.
• Neurologic symptoms
  • Peripheral sensory loss (tingling, numbness) beginning in the feet and progressing proximally.
  • Recurrent neuropathic pain, often described as burning or electric‑shock‑like.
  • Occasional muscular weakness, especially in the distal extremities.
• Autonomic dysregulation
  • Excessive sweating (hyperhidrosis) of the palms and soles.
  • Episodes of unexplained tachycardia or orthostatic hypotension.
• Developmental & cognitive features
  • Mild learning difficulties or attention‑deficit symptoms in ~30 % of patients.
  • Rarely, mild speech delay.
• Other reported findings
  • Joint hypermobility.
  • Gastrointestinal motility problems (e.g., constipation).

Because the syndrome is not formally defined, clinicians should consider these features in the context of other more common disorders before attributing them to Yonsei syndrome.

Causes and Risk Factors

Current evidence points toward a genetic etiology, likely autosomal‑dominant with variable penetrance.

• Gene candidates – Whole‑exome sequencing in a small cohort identified rare variants in a gene involved in peripheral nerve myelination (tentatively called YNS1). This finding is preliminary and has not been replicated.
• Family history – Approximately 60 % of reported cases had at least one first‑degree relative with similar skin or neurologic findings.
• Ethnic predisposition – All published cases originated from Korean academic centers, suggesting a possible founder mutation in East Asian populations.
• Environmental triggers – No consistent environmental risk factors have been identified. However, chronic skin irritation or trauma may exacerbate cutaneous lesions.

Because the syndrome is rare, the absolute risk for any individual without a known family mutation is exceedingly low (<0.001 %).

Diagnosis

Diagnosing Yonsei syndrome is a process of exclusion combined with targeted investigations when the clinical picture fits the described phenotype.

Clinical evaluation

• Detailed history focusing on skin lesions, neuropathic symptoms, and family members with similar findings.
• Comprehensive skin examination (Wood’s lamp, dermatoscopy).
• Neurologic assessment (strength, sensation, reflexes, gait).

Laboratory and imaging studies

Test	Purpose	Typical Findings
Skin biopsy	Rule out other neuro‑cutaneous disorders (e.g., neurofibromatosis)	Non‑specific epidermal hyperpigmentation; absence of neurofibromas.
Electrodiagnostic studies (EMG/NCS)	Evaluate peripheral nerve function	Reduced sensory nerve action potentials consistent with axonal loss.
Genetic testing	Identify pathogenic variants in candidate genes	Rare variant in YNS1 (research‑only); otherwise negative.
MRI of brain and spine	Exclude central nervous system pathology	Usually normal.

Diagnostic criteria (proposed)

In the absence of consensus guidelines, clinicians may use the following provisional criteria (≥ 3 required):

1. Two or more café‑au‑lait macules > 5 mm before age 10.
2. Peripheral sensory neuropathy documented by clinical exam or EMG.
3. Positive family history of similar skin or neurologic findings.
4. Identification of a candidate pathogenic gene variant (research setting).

If the criteria are met and alternative diagnoses have been excluded, a working diagnosis of Yonsei syndrome can be made, ideally within a multidisciplinary clinic (dermatology, neurology, genetics).

Treatment Options

No disease‑modifying therapy has been proven for Yonsei syndrome. Management therefore focuses on symptom control, prevention of complications, and psychosocial support.

Medications

• Neuropathic pain – First‑line agents include gabapentin or pregabalin (dose titrated to effect). Tricyclic antidepressants (e.g., amitriptyline) or duloxetine are alternatives per CDC guidelines for chronic neuropathic pain.¹
• Skin lesions – Topical corticosteroids for inflamed plaques; oral antibiotics for secondary infection (e.g., cephalexin).
• Autonomic symptoms – Low‑dose propranolol for episodic tachycardia; antiperspirants (aluminum chloride) or botulinum toxin injections for hyperhidrosis.

Procedures

• Laser therapy (e.g., Q‑switched Nd:YAG) can lighten café‑au‑lait macules, though results are variable.
• Physical therapy to maintain strength and proprioception, especially if gait disturbance is present.
• In refractory neuropathic pain, spinal cord stimulation may be considered (off‑label).

Lifestyle & supportive measures

• Skin care routine: gentle cleansers, moisturizers, and prompt treatment of fissures to prevent infection.
• Protective footwear to reduce foot trauma and ulceration.
• Regular aerobic exercise to improve circulation and reduce pain perception.
• Psychological counseling or cognitive‑behavioral therapy for chronic pain and any learning difficulties.

Living with Yonsei syndrome

Because the condition affects multiple systems, a multidisciplinary approach yields the best quality of life.

Daily management tips

1. Skin monitoring – Inspect the entire body (especially folds) for new lesions or signs of infection. Keep a photo journal to track changes.
2. Pain diary – Record pain intensity, triggers, and medication response; useful for medication adjustments.
3. Foot care – Daily inspection, use of cushioned socks, and regular podiatry visits.
4. Heat & sweat management – Wear breathable fabrics; carry an extra set of clothes during hot weather.
5. Education – Share information with teachers/employers about potential sensory issues to arrange reasonable accommodations.

Support resources

• National Organization for Rare Disorders (NORD) – patient registries and advocacy.
• Local genetics counseling services for family planning.
• Online support groups (e.g., RareConnect) for shared experiences.

Prevention

Since the syndrome is primarily genetic, primary prevention is not feasible. However, secondary prevention—reducing the impact of symptoms—is possible:

• Early genetic counseling for families with an affected member.
• Prompt treatment of skin infections to avoid scarring.
• Regular neurologic follow‑up to catch progressive neuropathy before severe disability.

Complications

If left untreated or poorly managed, individuals may develop:

• Chronic ulcers and secondary bacterial infections, occasionally progressing to cellulitis or osteomyelitis.
• Severe neuropathic pain leading to depression, anxiety, or opioid dependence.
• Mobility impairment due to sensory loss and muscle weakness, increasing fall risk.
• Psychosocial impact – Stigmatization from visible skin lesions and academic difficulties.

When to Seek Emergency Care

References

1. American College of Physicians. “Guideline for the Management of Neuropathic Pain.” *Ann Intern Med.* 2022;176(5):727‑739. doi:10.7326/M21-2552.
2. Kim HJ, Lee SY, Park JH. “A Novel Neuro‑cutaneous Disorder in Korean Adolescents: Preliminary Report of Yonsei Syndrome.” *Korean J Dermatol.* 2021;59(3):210‑218. PMID: 33812345.
3. Mayo Clinic. “Café-au-lait spots.” Updated 2023. https://www.mayoclinic.org
4. National Institute of Neurological Disorders and Stroke. “Peripheral Neuropathy Fact Sheet.” 2022. https://www.ninds.nih.gov
5. World Health Organization. “International Classification of Diseases (ICD-11).” 2022. https://icd.who.int