Case 1

[md90]

A 45-year-old man comes to a community health clinic for his annual physical. He has no major complaints other than his chronic arthritis, which is worsening and is affecting his lower back, hips, and knees. On physical examination, the patient's sclerae are note to be brownish-blue, and his ear cartilage is similarly discolored. An x-ray of the spine reveals disc degeneration and dense calcification that is most prominent in the lumbar region. Upon voiding for urinalysis, the man's urine is a normal color; however, after standing, the urine is dark.

1. What is the most likely diagnosis?
2. What is the biochemical defect in this condition?
3. From which essential amino acid is the accumulated metabolite involved in this defect derived?
4. Given this patient's extent of joint disease, how might his mental functioning be affected?
5. What is the most appropriate treatment for this condition?

[ZWobble]

1. The disease is Alkaptonuria

2. Defect in the enzyme homogentisate oxidase.
Which converts homogentisate to maleylacetoacetate (tyrosine metabolism)

3. Phenylalanine


I'm not sure about the last two....

[md90]

1. The disease is Alkaptonuria

2. Defect in the enzyme homogentisate oxidase.
Which converts homogentisate to maleylacetoacetate (tyrosine metabolism)

3. Phenylalanine


I'm not sure about the last two....

Good job zwobble!!!

A follow-up questions:
1. What is homogentisate normally metabolized to?
2. Is Phenylalanine ketogenic, glucogenic, or both?

In relation to the last two questions:
4. there is no effect on cognitive functioning.. it's a benign disease
5. the only thing that is recommended is to treat the patient's arthritis; can restrict the intake of tyrosine and phenylalanine in the diet BUT no benefit has been seen;

[MDiva]

Hmmm... homogentinsic acid metabolizes to melanin...?

Gotta get these cobwebs off!!!!

[md90]

Hmmm... homogentinsic acid metabolizes to melanin...?

Gotta get these cobwebs off!!!!

BREATHE!!! you are doing good... and that's what this forum is for.. to make your mistakes here... NOT on the actual exam.. :p

homogentisate normally metabolizes to acetaacetate (ketone) and fumarate (part of the TCA cycle);

phenylalanine is both ketogenic and glucogenic...

tyrosine goes to melanin via Dopa..

[MDiva]

homogentisate normally metabolizes to acetaacetate (ketone) and fumarate (part of the TCA cycle);

phenylalanine is both ketogenic and glucogenic...

tyrosine goes to melanin via Dopa..


Excellent...more please!