TSC is characterized by multisystem hamartomas, most commonly skin, brain, kidney, lung and heart, appearing at different ages. Skin involvement includes: hypomelanotic macules (ash leaf) present within the first years of life; angiofibromas that appear at age 3-4 years as erythematous and papulonodular lesions; ungual fibromas; cephalic and lumbar (shagreen patch) fibrous plaques; and "confetti" skin lesions appearing in childhood to early adolescence. Brain is involved in almost all cases of TSC, with the presence of different neuropathological lesions, such as cortico/subcortical tubers, radial migration lines, subependymal nodules, SEGA. SEGA can cause hydrocephalus (growth risk higher in the first 3 decades). Early-onset epilepsy (infantile spasms and/or focal seizures) is present in 85% of patients. Neuropsychiatric features (intellectual disability, attention-deficit/hyperactivity disorder, autism spectrum disorders (ASD), self-injury, anxiety and obsessive compulsive tendencies have also been reported. Renal angiomyolipomas (AML) develop during childhood with a higher risk of growth during adolescence and adulthood and manifest by pain, hematuria/retroperitoneal hemorrhage, abdominal masses, hypertension and renal failure. Lymphangioleiomyomatosis (LAM), multifocal micronodular pneumocyte hyperplasia (MMPH) and pulmonary cysts develop during adulthood and manifest with dyspnea, pneumothorax, or chylothorax. Cardiac rhabdomyomas (CR) appear during the fetal period and may become symptomatic (outflow tract obstruction or by interfering with valvular function) during infancy and early childhood. Additional features include dental enamel pitting, intraoral fibromas and skeletal dysplasias.
TSC is due to mutations in TSC1 (9q34) and TSC2 (16p13.3) which encode proteins that indirectly inhibit mTOR. In excess, mTOR causes disproportionate glutamate activity leading to disrupted synaptic plasticity.
