Скачать или смотреть 23. Disorders of Aromatic Amino Acid Metabolism | Tyrosinemia(Types I, II, III) Biochemistry USMLE

𝐒𝐮𝐛𝐬𝐜𝐫𝐢𝐛𝐞 𝗙𝐨𝐫 𝗠𝐨𝐫𝐞 𝗜𝐧𝐟𝐨𝐫𝐦𝐚𝐭𝐢𝐨𝐧 𝐨𝐧 𝗛𝐞𝐚𝐥𝐭𝐡 👩‍⚕‍ 𝐚𝐧𝐝 𝗠𝐞𝐝𝐢𝐜𝐢𝐧𝐞💉🩺💊
📌𝗜𝗻𝘀𝘁𝗮𝗴𝗿𝗮𝗺 :   / clinical.learning  

Disorders of Aromatic Amino Acid Metabolism | Tyrosinemia (Types I, II, III) | Medical Biochemistry | USMLE Step 1 MBBS

👋 Hey future doctors and biochem learners! Tyrosine is a key aromatic amino acid that gives rise to neurotransmitters, hormones, and pigments. But defects in its breakdown pathway can lead to a group of rare but serious disorders known as Tyrosinemias. These are classic inborn errors of metabolism and high-yield topics for MBBS, NEET PG, FMGE, and USMLE Step 1.

In this lecture, we’ll simplify the biochemical pathways, enzyme defects, clinical features, and management of Tyrosinemia Types I, II, and III. 🧬📚

🌟 Types of Tyrosinemia

1️⃣ Tyrosinemia Type I (Hepatorenal Tyrosinemia)

Defect: Fumarylacetoacetate hydrolase deficiency.

Accumulation: Succinylacetone & fumarylacetoacetate (toxic metabolites).

Clinical 🩺: Severe liver failure, renal tubular dysfunction (Fanconi-like), cabbage-like odor, high risk of hepatocellular carcinoma.

Treatment: Nitisinone (inhibits upstream step), dietary restriction of Phe & Tyr, liver transplantation in severe cases.

2️⃣ Tyrosinemia Type II (Oculocutaneous Tyrosinemia / Richner-Hanhart Syndrome)

Defect: Tyrosine aminotransferase deficiency.

Clinical 🩺: Photophobia, eye pain, keratitis, palmoplantar hyperkeratosis, intellectual disability.

Treatment: Low-tyrosine, low-phenylalanine diet.

3️⃣ Tyrosinemia Type III

Defect: 4-Hydroxyphenylpyruvate dioxygenase deficiency.

Clinical 🩺: Neurologic problems like seizures, ataxia, developmental delay.

Treatment: Dietary restriction of Tyr & Phe.

🧪 Diagnosis

Elevated plasma tyrosine.

Specific metabolites (e.g., succinylacetone in urine for Type I).

Genetic testing for enzyme defects.

⚙️ Clinical Integration

Type I: most severe; presents in infancy with liver failure.

Type II: mainly eye + skin involvement.

Type III: rare; neurological symptoms.

All three types show hyper-tyrosinemia but differ in presentation and enzyme block.

🎯 Exam Integration

Type I: fumarylacetoacetate hydrolase defect → liver + kidney disease.

Type II: tyrosine aminotransferase defect → eye + skin lesions.

Type III: 4-hydroxyphenylpyruvate dioxygenase defect → neurological symptoms.
👉 Commonly tested in case-based questions with clues like cabbage odor (Type I) or eye lesions (Type II).

👉 Don’t forget to Subscribe and hit the 🔔 bell for more high-yield biochemistry lectures!

👍 If this lecture helps you, give it a like and share it with your classmates. Your support keeps us motivated to create more simplified, exam-focused content. 🙌

❓Want us to cover a comparative summary of PKU, Alkaptonuria & Tyrosinemias in one chart for quick revision? Drop a comment below! 😊

#Tyrosinemia #AminoAcidMetabolism #AromaticAminoAcids #MedicalBiochemistry #USMLEStep1 #MBBSLectures #FMGE #NEETPG #FumarylacetoacetateHydrolase #Succinylacetone #RichnerHanhart #OculocutaneousTyrosinemia #LiverFailure #MetabolicDisorders #BiochemistryLecture #MedicalStudents