Question

In homocystinuria:

- Define it

- In a table write the types of homocystinuria

- Write types of homocystinuria & its associated enzyme

- Draw demonstrating homocystinuria disorder

Answer 1

Feature	Classical Homocystinuria	Methylcobalmin defect	MTHFR deficiency
Homocystinaemia	Present	Present	Present
Methionine level in blood	Increased	Not Increased	Not increased
Cystine level in blood	Decreased	Not Decreased	Not Decreased

Megaloblastic Anaemia

Absent

Present

Absent

Homocystinuria is an inherited group of disorder of metabolism of suphur containing amino acids methionine due to a deficiency of cystathionine beta synthase. It is inherited as autosomal recessive trait .

There are 2 types of Homocystinuria
a)Classical Homocystinuria - Deficiency of Cystathionine Beta synthase

b) Non classical Homocystinuria -
1. Defect in formation of N5 Methyl TetraHydroFolic acid (N5 MTHFR )

2.Defect in Methylcobalmin

Clinical features
1.Pectus carinatum
2. Pectus excavatum
3. Arachnodactyly
4. Knee deformities
5.Lens dislocation im downward direction
6.Thrombotic episodes like coronary artery disease and stroke like episodes because of increased Homocystine
7.Mental retardation
8.Resemble Marfan syndrome

Management
1.CYANIDE NITOPRUSIDE TEST - Magenta colour
2.Tandem Mass Spectrophotometry
3.Enzyme analysis
4. DNA study

TREATMENT :
1.High dise of vitamin B6 because it is coenzyme for PLP pyridoxal phosphate required for synthesis of cysthathione Beta synthase

2.Restriction of Methionine and cystine supplementation because methionine is syntheised and cysteine is not formed in body

3 .Betaine ( Trimethyl glycine ) for remethylation of Homocysteine

4.Vitamin C for endothelial function