Neurocutaneous disorders: Pathology review

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Neurocutaneous disorders: Pathology review



Neurocutaneous disorders: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 29-year-old man comes to the clinic due to headaches and feeling unstable. Over the past 6 months, the patient gradually has been falling more frequently. He has also been experiencing constant headaches which are worse in the morning. He denies any trauma and does not use alcohol illicit drugs. Medical history is notable for pheochromocytoma, treated with surgery 6 months ago. Vitals are within normal limits. On physical examination, he has difficulty ambulating or standing with feet close together. An MRI is obtained and shown below:  

Reproduced from: Wikimedia Commons    
Histopathological analysis of this patient's lesion would most likely show which of the following?  


At the family medicine clinic, a 17 year old male named Heath came in because of lower back pain. Clinical examination reveals lots of small growths on the face, light flat patches throughout his body, and a darker raised patch on his forehead. Heath was adopted early in his life and his family history is unknown. Abdominal ultrasound reveals an angiomyolipoma of the left kidney. Next to Heath, there’s an 8 year old child named Sylvia. Sylvia complains of difficulty seeing what the teacher is writing in school. She also has a purple mark that covers the forehead and her right upper eyelid. Eye examination reveals increased intraocular pressure in the right eye. Her medical history includes an episode of seizure when she was 5 years old. A brain MRI is ordered and reveals brain atrophy. Finally, there’s a 45 year old male named Austin who came in because of a ringing sound in his ears and a gradual loss of hearing. Brain MRI reveals bilateral masses on the cerebellopontine angle.

Okay, so all of them have a neurocutaneous syndrome. Neurocutaneous syndromes primarily affect the nervous system and the skin. They include Sturge-Weber syndrome, tuberous sclerosis, neurofibromatosis type I and II, and Von Hippel-Lindau disease. For the exams remember that Sturge-Weber occurs due to sporadic mutations, while tuberous sclerosis, neurofibromatosis type I and II, and Von Hippel-Lindau disease are autosomal dominant conditions.

Alright, now let’s take a closer look at these different disorders, starting with Sturge-Weber syndrome, which is also known as encephalotrigeminal angiomatosis. During week 6 of development, as the cephalic portion of the neural tube grows, a network of tiny blood vessels called a vascular plexus develops. There’s a gene called the GNAQ gene which codes for a guanine nucleotide-binding protein that is involved in the development of that plexus. Normally, around week 9, the GNAQ gene stops getting expressed, leading to the regression of the vascular plexus. But in Sturge-Weber syndrome, a sporadic mutation occurs that let some cells keep making GNAQ proteins. The mutated cell then replicates over and over, so all of the cells that descend from it have the mutation.


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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Rook's Textbook of Dermatology" Wiley-Blackwell (2004)
  4. "Ophthalmology" Elsevier Health Sciences (2009)
  5. "Practical Surgical Neuropathology" Elsevier Health Sciences (2010)
  6. "Adams and Victor's Principles of Neurology, Ninth Edition" McGraw Hill Professional (2009)
  7. "Fundamentals of Pathology" H.A. Sattar (2011)
  8. "von Hippel–Lindau disease: A clinical and scientific review" European Journal of Human Genetics (2011)
  9. "Sturge-Weber syndrome: A review" Pediatric Neurology (2004)
  10. "Genotype-Phenotype Correlation in von Hippel-Lindau Disease With Retinal Angiomatosis" Archives of Ophthalmology (2007)

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