Neurology syndromes.

Gene/chromosome: GNAQ, chromosome 9; Inheritance: Sporadic somatic mosaicism; Triad: Facial port-wine stain, leptomeningeal angioma, seizures; Associated: Glaucoma, intracranial calcification; Investigation: MRI with contrast, tram-track calcification on CT

Gene/chromosome: TSC1 chromosome 9, TSC2 chromosome 16; Inheritance: Autosomal dominant; Triad: Seizures, intellectual disability, facial angiofibromas; Associated: Renal angiomyolipoma, cardiac rhabdomyoma; Investigation: MRI brain showing cortical tubers/subependymal nodules

Gene/chromosome: NF1, chromosome 17; Inheritance: Autosomal dominant; Triad: Café-au-lait macules, neurofibromas, axillary freckling; Associated: Optic pathway glioma, pheochromocytoma, malignant peripheral nerve sheath tumor; Investigation: NF1 criteria, slit-lamp Lisch nodules

Gene/chromosome: NF2, chromosome 22; Inheritance: Autosomal dominant; Triad: Bilateral vestibular schwannomas, hearing loss, tinnitus; Associated: Meningioma, ependymoma; Investigation: MRI internal auditory canals

Gene/chromosome: VHL, chromosome 3; Inheritance: Autosomal dominant; Triad: Retinal hemangioblastoma, CNS hemangioblastoma, renal cell carcinoma; Associated: Clear-cell RCC, pheochromocytoma, pancreatic cysts; Investigation: VHL genetic testing, MRI, retinal examination

Gene/chromosome: HTT, chromosome 4; Inheritance: Autosomal dominant, CAG expansion; Triad: Chorea, psychiatric changes, progressive dementia; Associated: Caudate atrophy; Investigation: HTT CAG-repeat testing

Gene/chromosome: FXN, chromosome 9; Inheritance: Autosomal recessive, GAA expansion; Triad: Ataxia, loss of proprioception, absent ankle reflexes; Associated: Hypertrophic cardiomyopathy, diabetes; Investigation: FXN genetic testing, ECG/echo

Gene/chromosome: ATP7B, chromosome 13; Inheritance: Autosomal recessive; Triad: Hepatic disease, neuropsychiatric symptoms, Kayser-Fleischer rings; Associated: Hemolytic anemia, cirrhosis; Investigation: Low ceruloplasmin, increased urinary copper, slit-lamp examination

Gene/chromosome: ATM, chromosome 11; Inheritance: Autosomal recessive; Triad: Cerebellar ataxia, telangiectasia, recurrent infections; Associated: Increased leukemia/lymphoma risk, elevated AFP; Investigation: ATM testing, AFP, immunoglobulins

Gene/chromosome: MECP2, chromosome X; Inheritance: X-linked dominant, usually females; Triad: Developmental regression, loss of purposeful hand use, stereotypic hand movements; Associated: Seizures, breathing abnormalities, scoliosis; Investigation: MECP2 genetic testing

Gene/chromosome: HPRT1, chromosome X; Inheritance: X-linked recessive; Triad: Hyperuricemia, dystonia, self-injurious behavior; Associated: Gout, nephrolithiasis; Investigation: HPRT enzyme activity or genetic testing

Gene/chromosome: ATP7A, chromosome X; Inheritance: X-linked recessive; Triad: Kinky hair, developmental delay, seizures; Associated: Connective tissue abnormalities, failure to thrive; Investigation: Low serum copper/ceruloplasmin, ATP7A testing

Gene/chromosome: HEXA, chromosome 15; Inheritance: Autosomal recessive; Triad: Developmental regression, exaggerated startle, cherry-red macula; Associated: Progressive neurodegeneration; Investigation: Hexosaminidase A deficiency

Gene/chromosome: SMPD1, chromosome 11; Inheritance: Autosomal recessive; Triad: Hepatosplenomegaly, neurodegeneration, cherry-red macula; Associated: Foam cells, progressive neurologic decline; Investigation: Acid sphingomyelinase activity

Gene/chromosome: ASPA, chromosome 17; Inheritance: Autosomal recessive; Triad: Macrocephaly, hypotonia, developmental regression; Associated: Spongiform degeneration of white matter; Investigation: Increased N-acetylaspartate on MR spectroscopy

Gene/chromosome: ABCD1, chromosome X; Inheritance: X-linked; Triad: Progressive behavioral changes, cognitive decline, spasticity; Associated: Adrenal insufficiency, cerebral demyelination; Investigation: Very-long-chain fatty acids, ABCD1 testing

Gene/chromosome: SCN1A, chromosome 2; Inheritance: Usually de novo; Triad: Infantile-onset prolonged febrile seizures, multiple seizure types, developmental impairment; Associated: Drug-resistant epilepsy; Investigation: SCN1A genetic testing