1. Multidisciplinary detective work
S Jarvis, (Pharmacy), A Bowron, V Powers (Clinical Biochemistry) and G Pierre (Paediatric Metabolic Medicine)
Bristol Royal Hospital for Children
This is an example of multi-disciplinary work that had some good outcomes but probably the evidence wouldn’t stand up in court

2. Case History AB is a girl born in February 2009
NICU for 2 weeks, hypotonia, and difficult feeding
8 episodes of becoming floppy, eyes rolling, breathing difficulties
July 2009 needed increasing respiratory support
27th July 2009 admitted to PICU for ventilation
Because of her progressive illness she underwent many tests for a variety of conditions but I want to concentrate on just one aspect of her investigations and treatment.

3. Metabolic Investigations April - September 2009
Persistent lactic acidosis
Plasma amino acids normal
Urine organic acids showed
lactic acid
3-methylglutaconic acid in 2 out of 6 samples
Muscle biopsy could not exclude mitochondrial DNA depletion syndrome
3-methylglutaconic acid in 2 out of 6 samples - an indication of a mitochondrial disorder
Mitochondria generate more than 90% of the energy required by the body. Mitochondrial dysfunction depletes cells of energy causing cell damage and even cell death. Due to the high energy requirements of brain and muscle, mitochondrial disease typically affect these parts of the body causing encephalomyopathies (brain and muscle disease).
Mitochondrial DNA Depletion Syndrome are progressive disorders often fatal in childhood and for which no specific or effective therapy is available.

4. Treatment - September 2009 Dichloroacetate (DCA) started
DCA interacts with the pyruvate dehydrogenase enzyme complex located in the mitochondria
Used for the treatment of lactic acidosis in patients with pyruvate dehydrogenase defects
Side effect profile includes polyneuropathy on prolonged use

5. November a 2nd opinion
Repeat organic acid analysis showed markedly increased maleic acid and succinylacetone both toxic metabolites of the tyrosine metabolic pathway
Recommended starting nitisinone to remove the maleic acid and succinylacetone
? Initial diagnosis of tyrosinaemia
To return to the patient

6. Back in Bristol Review of previous results
No succinylacetone in previous samples
Trace of derivatives in 2 samples
Liver Function and clotting normal
Tyrosine not increased
Clinical presentation not typical of tyrosinaemia
Nitisinone and low tyrosine diet started in November initially for a short trial

7. Nitisinone
Nitisinone inhibits enzymatic activity blocking the formation of fumarylacetoacetate and succinylacetone
Nitisinone started based on a previously reported case in which
“the morning after starting treatment ……. instead of just being able to walk with a wide-based unsteady gait, she could walk quite rapidly and steadily and could walk downstairs; a few days later she was able to run”

8. Further discussions
? Did dichloroacetate exacerbate an underlying enzyme defect
Was the maleic acid also present in previous samples?
? diagnosis of inherited deficiency of maleylacetoacetate isomerase (MAAI)
No abnormality was found on sequencing MAAI gene
Did Dichloroacetate exacerbate an underlying enzyme defect and also cause a deterioration in her clinical condition because of a polyneuropathy
maleylacetoacetate isomerase (MAAI) - the first known case

9. Nitisinone Tyrosine 4-OH-phenylpyruvate Homogentisate Maleic acid
Tyrosine degradation pathway
Tyrosine
4-OH-phenylpyruvate
Nitisinone
Homogentisate
Dichloroacetate
Maleic acid
Maleylacetoacetate X
Succinylacetoacetate
MAAI
Tyrosine
A semi-essential amino acid incorporated into proteins or degraded into 2 product fumarate and acetoacetate which feeds into the Krebs (citric acid) cycle. Defects in tyrosine metabolic pathways lead to an accumulation of tyrosine and also accumulation of some of the products of alternative pathways such as succinylacetone which is potentially the toxic metabolite which lead to liver and renal tubular disorders.
Repeat organic acid analysis showed markedly increased maleic acid and succinylacetone both toxic metabolites of the tyrosine metabolic pathway
? diagnosis of inherited deficiency of maleylacetoacetate isomerase (MAAI)
Fumarylacetoacetate
Succinylacetone
Fumarate
Acetoacetate
Porpho-
bilinogen
5-ALA

10. Meanwhile - Another case?
A second patient underwent tests for metabolic disease and was also shown to have maleic acid in her urine.
On re-testing 2 months later this had disappeared without treatment
This patient was not on DCA and had a different presentation from AB
The clinical biochemist asked for information about her drug history as her notes were difficult to follow
After some investigation she was shown to have been previously prescribed domperidone for a short period
Domperidone was thought to be relevant as prescribed initially but no longer being taken by the time of the repeat tests.

11. Following up on patient AB
A review of treatment was also undertaken for AB
Relevant findings
Age 4-6 months domperidone
Age 6-7 months amlodipine

12. Maleate salts Used in several common drugs including
Domperidone
Amlodipine
Enalapril
So were these the cause of AB’s metabolic findings?
Comment on cardiacs and cardiomyopathy screen

13. Hypothesis
Could these patients have a polymorphism in a drug metabolising enzyme causing slow metabolism of maleic acid.
This would cause small increases in maleic acid
The addition of dichloroacetate in patient AB impaired MAAI activity resulting in a more marked increase in maleic acid

14. If so………….. Can we stop the low tyrosine diet and Nitisinone?
Decision made to stop both and to monitor clinical and biochemical changes
During the time that AB was on the treatment there had been no more abnormal findings relating to maleic acid or succinylacetone

15. However, looking further
Both patients were given domperidone liquid which is base not maleate
Only some brands of amlodipine are maleate salts and we don’t have a record of which one was given to AB
So we don’t have the evidence but……

16. Situation now AB has stopped Nitisinone since November 2010
No deterioration in clinical state
No return of maleic acid or succinylacetone
Markers of mitochondrial dysfunction still persist

17. AB
Clinically AB remains ventilator dependent and has just been discharged home with a “home ventilation” package
She continues on a metabolic cocktail of vitamins with no definitive diagnosis

18. Costs
£43,500 was spent on Nitisinone in the 12 months that AB was taking it
Biochemical monitoring cost approximately £4000
Additional genetic testing

19. Lessons learnt for pharmacists
Organic acid abnormalities secondary to drugs, including salts, are common
A full drug history is needed when interpreting complex metabolic investigations
Liaising with clinical biochemists when test are being done will help to arrive at more accurate diagnoses

20. Benefits in this case were that
Patient has been able to stop a “lifelong” treatment
The trust and PCT have saved £43,500 a year for Nitisinone

21. Thank you To the team of clinical biochemists To the Metabolic service
To the parents of “AB”
for all their support