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Features include: Focal impaired awareness seizure, Difficulty with thinking and memory (cognitive impairment), Focal cortical dysplasia type II, and Focal white matter lesions and 5 more.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 4 | Focal impaired awareness seizure, Difficulty with thinking and memory (cognitive impairment), Focal white matter lesions |
To date, at least 100 individuals have been identified with a pathogenic variant in MTOR leading to SKS [, , , , , , , , , , , , , , , , ]. The following description of the phenotypic features associated with this condition is based on these reports. Table 2. Smith-Kingsmore Syndrome: Frequency of Select Features
Feature | % of Persons w/Feature | Comment |
|---|---|---|
Developmental delay/ intellectual disability | 89/94 (95%) | Most commonly in the moderate-to-severe range |
Developmental regression observed in 18% Macrocephaly | 88/98 (90%) | — |
Distinctive facial features | 57/72 (79%) | Recognizable for persons w/pathogenic variants in FAT kinase domains (See .) |
Brain malformations | 65/82 (79%) | Incl megalencephaly, agenesis or hypogenesis of corpus callosum, cortical malformations, generalized white matter loss w/accompanying ventriculomegaly (ex vacuo) |
Neuromuscular concerns | 48/61 (79%) | Incl hypotonia |
Sleep-wake abnormalities | 27/35 (77%) | Incl insomnia, obstructive sleep apnea, circadian rhythm sleep-wake phase disorder |
Ophthalmologic problems | 34/48 (71%) | Incl strabismus, refractory abnormalities, optic atrophy |
Skeletal abnormalities | 29/45 (64%) | Most commonly scoliosis |
Epilepsy | 48/79 (61%) | Generalized, focal, or status epilepticus |
Generalized overgrowth | 28/59 (47%) | Mostly in early childhood; not a prominent feature in adulthood |
Autism | 36/79 (46%) | — |
Hyperphagia | 11/27 (41%) | Early onset |
Cardiovascular problems | 18/45 (40%) | Incl valvar abnormalities, septal defects, aortic root dilatation |
ADHD/hyperactivity | 11/49 (22%) | Developmental delays and intellectual disability. The majority of affected individuals exhibit developmental delays, which are often the first noticeable feature, typically presenting before the age of two years. |
Source: GeneReviews — "Smith-Kingsmore Syndrome"
MTOR encodes mechanistic target of rapamycin kinase (2,549 aa). Serine/threonine protein kinase which is a central regulator of cellular metabolism, growth and survival in response to hormones, growth factors, nutrients, energy and stress signals. Highest expression in Testis (35.5 TPM) and Brain Cerebellum (27.1 TPM).
Isolated focal cortical dysplasia type II is associated with mutations in the MTOR gene on chromosome 1.
The MTOR protein participates in Energy dependent regulation of mTOR by LKB1-AMPK, mTORC1-mediated signalling, and Amino acids regulate mTORC1 pathways.
MTOR is classified as a druggable target (Clinically Actionable, Drug Resistance, Druggable Genome, Enzyme, Kinase, Phosphatidylinositol 3 Kinase, Serine Threonine Kinase, and Tyrosine Kinase categories) with score 0.7.
TSC1 function has not been fully characterized.
Isolated focal cortical dysplasia type II is associated with mutations in the TSC1 gene on chromosome 9.
TSC2 function has not been fully characterized.
Isolated focal cortical dysplasia type II is associated with mutations in the TSC2 gene on chromosome 16.
No consensus clinical diagnostic criteria for Smith-Kingsmore syndrome (SKS) have been published.
SKS should be considered in probands with the following clinical and brain MRI findings and family history.
Clinical findings
Source: GeneReviews — "Smith-Kingsmore Syndrome"
Genetic disorders characterized by macrocephaly, global developmental delays, hypotonia, seizures, sleep disturbance, and brain abnormalities are of interest in the differential diagnosis of Smith-Kingsmore syndrome (SKS) .
Table 3.
Smith-Kingsmore Syndrome: Differential Diagnosis
Gene(s)/ Genetic Mechanism | Disorder | MOI | Features of Disorder
Overlapping w/SKS | Distinguishing from SKS
CHD3 | Snijerds Blok-Campeau syndrome (OMIM 618205) | AD | • Macrocephaly
DD
Hypotonia
| • Midface hypoplasia, dental abnormalities
Cutaneous findings
Absence of overgrowth
NSD1 | Sotos syndrome | AD | • Macrocephaly
Autistic features
DD
Hypotonia
Cardiovascular anomalies
| • Characteristic features incl dolichocephaly prognathism
Advanced bone age
|
PIK3CA
Source: GeneReviews — "Smith-Kingsmore Syndrome"
Genetic testing for MTOR, TSC1, TSC2 is available. Testing is considered confirmatory for diagnosis.
Biomarker and diagnostic research for isolated focal cortical dysplasia type II has been reported in the published literature.
No approved treatments are currently available for isolated focal cortical dysplasia type II. The disease remains an area of unmet medical need.
Gene therapy approaches for isolated focal cortical dysplasia type II have been reported in the published literature.
No clinical practice guidelines for Smith-Kingsmore syndrome (SKS) have been published. In the absence of published guidelines, the following recommendations are based on the authors' personal experience managing individuals with this disorder.
To establish the extent of disease and needs in an individual diagnosed with SKS, the evaluations summarized (if not performed as part of the evaluation that led to diagnosis) are recommended.
Table 4.
Smith-Kingsmore Syndrome: Recommended Evaluations Following Initial Diagnosis
System/Concern | Evaluation | Comment
Constitutional
| Measurement of growth parameters incl head circumference | • To assess for macrocephaly generalized overgrowth
To assess for obesity in those who have hyperphagia
| Neurologic eval | • Brain MRI should be considered to identify any brain malformations.
Baseline EEG given high frequency of seizures
| Developmental assessment | • To incl motor, adaptive, cognitive, feeding, speech-language eval
Eval for early intervention/ special education
Neurobehavioral/
| Neuropsychiatric eval | • Formal autism eval in those w/findings suggestive of ASD
For persons age 12 mos: screening for ADHD, anxiety, aggression, self-injury
| • Clinical assessment for scoliosis /or pes planus
Consider radiographs in those who have clinical scoliosis.
Orthopedics/ physical medicine rehab/ PT OT eval
| To incl assessment of:
Source: GeneReviews — "Smith-Kingsmore Syndrome"
1 trial found
To monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations, the evaluations summarized in are recommended. Table 6. Smith-Kingsmore Syndrome: Recommended Surveillance
System/Concern | Evaluation | Frequency |
|---|---|---|
Psychiatric | Assessment for anxiety, ADHD, ASD, aggression, self-injury | As clinically indicated |
Musculoskeletal | Assessment of mobility self-help skills | At each visit Clinical assessment for scoliosis |
Eyes | Ophthalmology eval | At least annually, or as clinically indicated or recommended by ophthalmologist |
Hearing | Audiology eval | As clinically indicated |
Respiratory | Monitor for signs/symptoms of sleep disturbance. | At each visit |
Endocrine | Monitor for hypoglycemia. | As clinically indicated, primarily in infancy |
Family/Community | Assess family need for social work support (e.g., palliative/respite care, home nursing, other local resources), care coordination, or follow-up genetic counseling if new questions arise (e.g., family planning). | At each visit ADHD = attention-deficit/hyperactivity disorder; ASD = autism spectrum disorder |
Source: GeneReviews — "Smith-Kingsmore Syndrome"
Estimated prevalence: Unknown (Unknown prevalence).
1 clinical trial registered. Interventions under study include drug therapy. Pipeline includes 1 PHASE1. Research is primarily industry-sponsored.
76 publications have been identified in PubMed for isolated focal cortical dysplasia type II. Research spans Basic Science / Preclinical (47%), Epidemiology / Natural History (12%), and Diagnostic / Biomarker (11%).
Research Type | Count | % of Total |
|---|---|---|
Laboratory research | 36 | 47% |
Disease patterns and progression | 9 | 12% |
Testing and diagnosis research | 8 | 11% |
Clinical study results | 8 | 11% |
Research summaries | 6 | 8% |
Patient case studies | 5 | 7% |
New treatment approaches | 4 | 5% |
Mahmoud MB (2026). [PMID: 41352305](https://pubmed.ncbi.nlm.nih.gov/41352305/). *Clin Neurophysiol*. [Epidemiology / Natural History]
Kravutske Y (2026). [PMID: 41587495](https://pubmed.ncbi.nlm.nih.gov/41587495/). *Biomed Phys Eng Express*. [Diagnostic / Biomarker]
Maletic M (2026). [PMID: 41789478](https://pubmed.ncbi.nlm.nih.gov/41789478/). *Brain*. [Basic Science / Preclinical]
Pehlivan D (2026). [PMID: 41734767](https://pubmed.ncbi.nlm.nih.gov/41734767/). *Am J Hum Genet*. [Basic Science / Preclinical]
Zhang Y (2026). [PMID: 42068085](https://pubmed.ncbi.nlm.nih.gov/42068085/). *Clin Transl Med*. [Basic Science / Preclinical]
Wu J (2026). [PMID: 42106671](https://pubmed.ncbi.nlm.nih.gov/42106671/). *BMC Neurol*. [Epidemiology / Natural History]
Garbelli R (2026). [PMID: 41636633](https://pubmed.ncbi.nlm.nih.gov/41636633/). *Neuropathol Appl Neurobiol*. [Review / Meta-Analysis]
Khazali MF (2026). [PMID: 41557258](https://pubmed.ncbi.nlm.nih.gov/41557258/). *Epilepsia Open*. [Basic Science / Preclinical]
Minguillón Pereiro AM (2026). [PMID: 42044938](https://pubmed.ncbi.nlm.nih.gov/42044938/). *Neurologia (Engl Ed)*. [Epidemiology / Natural History]
Rius R (2026). [PMID: 41951959](https://pubmed.ncbi.nlm.nih.gov/41951959/). *Nat Genet*. [Basic Science / Preclinical]
Data assembled from 8 of 12 sources · Last updated Sep 19, 2026, 9:43 PM UTC
Online Mendelian Inheritance in Man
European rare disease database
Genetic and Rare Diseases Info Center