Tuberous Sclerosis

December 31, 2006

A 10-year-old boy presents with abdominaldistension that has progressed slowlyfor the past 2 years. The distension,which is painless, does not impair hisdaily activities. He has not observedany changes in bowel or voiding habits.

A 10-year-old boy presents with abdominaldistension that has progressed slowlyfor the past 2 years. The distension,which is painless, does not impair hisdaily activities. He has not observedany changes in bowel or voiding habits.The child's medical history is significantfor poorly controlled generalizedtonic-clonic seizures, which beganaround his first birthday. At that time,he had several seizures each week.Neither phenytoin nor carbamazepinereduced the seizure frequency.The patient now attends a specialeducation class in a local elementaryschool after repeating grade 1.The child is a slender male inthe 50th percentile for weight and the25th percentile for height and head circumference.His face is covered withan acneiform eruption over both cheeksand around the mouth. The gumsshow fleshy gingival masses (Figure 1).A 3 * 5-cm hypopigmented area ispresent in the right axilla (Figure 2),and parts of the left gluteal area arecovered by a large, raised, irregulararea of thickened skin (Figure 3). Severalcaf au lait spots are present onhis back (Figure 4). The right first toeshows a fleshy outgrowth from the edgeof the nail bed (Figure 5).The abdomen is significantly distended.Ascites is not present. Largemultilobulated, nontender flank massesare palpated bilaterally. Neurologic examinationreveals developmental delaybut no focal neurologic deficits.The CT scan of the head showsmultiple subependymal calcificationsextending into both lateral ventricles(Figure 6). The CT of the abdomen revealsbilateral renal cysts with distortionof the calyceal architecture(Figure 7). Blood tests demonstratenormal renal function.TUBEROUS SCLEROSISThis child demonstrates thetypical features of tuberoussclerosis (TS) together withsome less common manifestationsof the disease. TS is adominantly inherited condition withreduced penetrance (about 50%). Itaffects 1 in 5000 to 1 in 10,000 personsworldwide. The gene defects arelocated on 9q34 (TSC-1) and 16p13.3(TSC-2), the sites for the tumor-suppressorgenes hamartin and tuberin.The clinical triad consists of angiofibromas,mental retardation, andseizures.Hypopigmented patches typicallycan be found at birth in 80% to 100%of those affected (see Figure 2), andmay be called "ash leaf spot,""thumbprint" or "confetti" lesions accordingto their configuration. Facialadenoma sebaceum (see Figure 1)and shagreen patches (ie, connectivetissue nevi) (Figure 3) develop inearly childhood. Gingival angiofibromas(see Figure 1) and periungual fibromas(see Figure 5) tend to occurlater and are not usually seen in children.Caf au lait spots (see Figure 4)can be found in about 5% of affectedpatients.Visceral changes typically involvethe heart (rhabdomyomas), theeyes (retinal hamartomas), the lungs(cysts, fibrosis, pneumothorax),and the kidneys (angiolipomas). Renalcysts (see Figure 7) are less common.Chronic renal insufficiency andhypertension may develop later inadulthood.The clinical CNS findings consistof seizures, which are typically difficultto control, and mental retardationwith developmental delay. Generally,the earlier the clinical onset, the moresevere the level of mental retardation.Imaging studies can identify subependymalnodules with calcificationsprojecting from the walls of the lateralventricles into the ventricular cavities(Figure 6), as well as sclerotic patches(tubers) in the hemispheric convolutions.Histologically, tubers consistof astrocyte proliferations togetherwith multinucleated giant neuronsthat replace the normal neuronalarchitecture.Treatment is supportive and consistsof seizure control, and the managementof renal failure and hypertensionlater in life. The obstructionof the foramen of Monro by a tuberwarrants urgent surgical intervention.Genetic counseling is imperative, andmust take into consideration that,although it is autosomal dominant,TS has a wide spectrum of clinicalpenetrance.

References:

FOR MORE INFORMATION:

  • Hyman MH, Whittemore VH. National Institutesof Health Conference: tuberous sclerosis complex.Arch Neurol. 2000;57:662-665.
  • Jozwiak S, Schwartz RA, Janniger CK, Bielicka-Cymerman J. Usefulness of diagnostic criteria oftuberous sclerosis complex in pediatric patients.J Child Neurol. 2000;15:652-659.