Autosomal Dominant Diseases Flashcards
Achondroplasia
Cell-signaling defect of fibroblast growth factor (FGF) receptor 3. Results in dwarfism; short limbs, larger head, but trunk size is normal. Associated with advanced paternal age.
Autosomal-dominant polycystic kidney disease (ADPKD)
Formerly known as adult polycystic kidney disease. Always bilateral, massive enlargement of kidneys due to multiple large cysts. Patients present with flank pain, hematuria, hypertension, progressive renal failure. 85% of cases are due to mutation in PKD1 (chromosome 16; 16 letters in “polycystic kidney”). Associated with polycystic liver disease, berry aneurysms, mitral valve prolapse. Infantile form is recessive.
Familial adenomatous polyposis
Colon becomes covered with adenomatous polyps after puberty. Progresses to colon cancer unless colon is resected. Mutations on chromosome 5 (APC gene); 5 letters in “polyp”.
Familial hypercholesterolemia (hyperlipidemia type IIA)
Elevated LDL due to defective or absent LDL receptor. Heterozygotes (1:500) have cholestrol about 300 mg/dL. Homozygotes (very rare) have cholestrol about 700+ mg/dL, severe atherosclerotic disease early in life, and tendon xanthomas (classically in the Achilles tendon); MI may develop before age 20.
Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome)
Inherited disorder of blood vessels. Findings: telangiectasia, recurrent epistaxis, skin discolorations, arteriovenous malformations (AVMs). Nosebleeds, acute + chronic digestive tract bleeding.
Treatments: Surgeries, iron, blood transfusions.
Hereditary spherocytosis
Spheroid erythrocytes due to spectrin or ankyrin defect; hemolytic anemia; Increased MCHC. Splenectomy is curative.
Huntington’s disease
Findings: depression, progressive dementia, choreiform movements, caudate atrophy, and decreased levels of GABA and ACh in the brain. Symptoms manifest in affected individuals between the ages of 20 and 50. Gene located on chromosome 4; trinucleotide repeat disorder: (CAG)n. “Hunting 4 food”.
Marfan’s syndrome
Fibrillin-1 gene mutations: connective tissue disorder affecting skeleton, heart and eyes. Findings: tall with long extremities, pectus excavatum, hypermobile joints, and long, tapering fingers and toes (arachnodactyly); cystic medial necrosis of aorta: aortic incompetence and dissecting aortic aneurysms; floppy mitral valve. Subluxation of lenses.
Multiple endocrine neoplasias (MEN)
Several distinct syndromes (1, 2A, 2B) characterized by familial tumors of endocrine glands, including those of the pancreas, parathyroid, pituitary, thyroid, and adrenal medulla MEN 2A and 2B are associated with ret gene.
MEN1 : pituitary, parathyroid, pancreas
MEN2A: medullary thyroid Ca, pheochromocytoma, parathyroid
MEN2B: medullary thyroid Ca, pheochromocytoma, Marfanoid, mucosal neuroma
Neurofibromatosis type 1 (Von Recklinghausen’s disease)
Findings: Cafe’-au-lait spots, neural tumors, Lisch nodules (pigmented iris hamartomas). Also marked by skeletal disorders (e.g., scoliosis) and optic pathway gliomas. On long arm of chromosome 17: 17 letters in “von Recklinghausen”.
Neurofibromatosis type 2
Bilateral acoustic schwannomas, juvenile cataracts. NF2 gene on chromosome 22; type 2 = 22.
Tuberous sclerosis
Findings: facial lesions (adenoma sebaceum), hypopigmented “ask leaf spots” on skin, cortical and retinal hamartomas, seizures, mental retardation, renal cysts and renal angiomyolipomas, cardiac rhabdomyomas, increased incidence of astrocytomas. Incomplete penetrance, variable presentation.
von Hippel-Lindau disease
Findings: hemangioblastomas of retina/cerebellum/medulla; the majority of affected individuals develop multiple bilateral renal cell carcinomas and other tumors. Associated with deletion of VHL gene (tumor suppressor) on chromosome 3 (3p). Results in constitutive expression of HIF (transcription factor) and activation of angiogenic growth factors. Von Hippel-Lindua = 3 words for chromosome 3.
