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AADC deficiency may be misdiagnosed or go undiagnosed, delaying treatment and proper management1-3

Despite symptom onset during infancy, diagnosis is typically delayed1

Mean age of diagnosis
3.5 years1

Age range of diagnosis
2 months to 23 years1

The challenge of a correct diagnosis: conditions with symptoms similar to those of AADC deficiency

AADC deficiency symptoms1,3 May be diagnosed as4-8
Oculogyric crisis Epilepsy
Dystonia
Rigidity
Motor delay		 Cerebral palsy
Dystonia
Developmental delay
Rigidity		 Juvenile parkinsonism
Hypotonia
Akinesia
Ptosis		 Neuromuscular disorders

Both juvenile parkinsonism and AADC deficiency are associated with a deficiency in dopamine, but they differ in etiology and presentation. Unlike juvenile parkinsonism, AADC deficiency is a nonprogressive, neurodevelopmental, single-gene disorder with symptom onset during infancy.1,8-10

You may want to consider an alternate diagnosis of a neurotransmitter disorder such as AADC deficiency for your patients with:

  • Cerebral palsy of unknown etiology
  • Epilepsy that is refractory to treatment
  • Juvenile parkinsonism whose symptoms don’t progress

WATCH: Learn more about common misdiagnoses of AADC deficiency

Keith Hyland, PhD, details common misdiagnoses of AADC deficiency and explains what physicians should look for to differentiate AADC deficiency from other conditions

Look for key differentiating signs and symptoms of AADC deficiency

One or a combination of the following red-flag diagnostic clues should prompt investigation for a neurotransmitter disorder, including AADC deficiency:

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Oculogyric crises2,3,11
Episodes of sustained upward or lateral deviation of the eyes, rhythmic orofacial movements, backward and lateral flexions of the neck, tongue protrusion, and jaw spasms that can sometimes be confused with seizures9,10

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History of normal EEG and neuroimaging inconsistent with presentation1,3,6,12
One study showed that only a small proportion of patients with AADC deficiency had an abnormal EEG, MRI, or CT2

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Autonomic symptoms3
Multiple signs of autonomic dysfunction12

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Diurnal variation1,4,14
Symptoms become exacerbated or more prominent late in the day and improve with sleep4,14

If you suspect your patient may have one or a combination of these distinguishing signs and symptoms, consider testing for AADC deficiency.

CT=computed tomography; EEG=electroencephalogram; MRI=magnetic resonance imaging.

Find out how to diagnose AADC deficiency

References: 1. Wassenberg T, Molero-Luis M, Jeltsch K, et al. Consensus guideline for the diagnosis and treatment of aromatic l-amino acid decarboxylase (AADC) deficiency. Orphanet J Rare Dis. 2017;12(1):12. doi: 10.1186/s13023-016-0522-z. 2. Brun L, Ngu LH, Keng WT, et al. Clinical and biochemical features of aromatic L-amino acid decarboxylase deficiency. Neurology. 2010;75(1):64-71. 3. Himmelreich N, Montioli R, Bertoldi M, et al. Aromatic amino acid decarboxylase deficiency: molecular and metabolic basis and therapeutic outlook. Mol Genet Metab. 2019;127(1):12-22. doi: 10.1016/j.ymgme.2019.03.009. 4. Ng J, Papandreou A, Heales SJ, et al. Monoamine neurotransmitter disorders—clinical advances and future perspectives. Nat Rev Neurol. 2015;11(10):567-584. 5. Lee W-T. Disorders of monoamine metabolism: inherited disorders frequently misdiagnosed as epilepsy. Epilepsy Seizure. 2010;3(1):147-153. doi: 10.3805/eands.3.147. 6. Kurian MA, Dale RC. Movement disorders presenting in childhood. Continuum (Minneap Minn). 2016;22(4):1159-1185. 7. Krigger KW. Cerebral palsy: an overview. Am Fam Physician. 2006;73(1):91-100. 8. Niemann N, Jankovic J. Juvenile parkinsonism: Differential diagnosis, genetics, and treatment. Parkinsonism Relat Disord. 2019;67:74-89. doi:10.1016/j.parkreldis.2019.06.025. 9. Shrimanker I, Tadi P, Sánchez-Manso JC. Parkinsonism. StatPearls [Internet]. StatPearls Publishing; 2022. https://www.ncbi.nlm.nih.gov/books/NBK542224/?report=classic. Updated 2022 May 8. Accessed July 2022. 10. Hwu PW, Kiening K, Anselm I, et al. Gene therapy in the putamen for curing AADC deficiency and Parkinson’s disease. EMBO Mol Med. 2021;13(9):e14712. doi:10.15252/emmm.202114712. 11. Pearson TS, Gilbert L, Opladen T, et al. AADC deficiency from infancy to adulthood: symptoms and developmental outcome in an international cohort of 63 patients. J Inherit Metab Dis. 2020;43(5):1121-1130. doi: 10.1002/jimd.12247. 12. Zouvelou V, Yubero D, Apostolakopoulou L, et al. The genetic etiology in cerebral palsy mimics: the results from a Greek tertiary care center. Eur J Paediatr Neurol. 2019;23(3):427-437. doi: 10.1016/j.ejpn.2019.02.001. 13. Hwu W-L, Lee N-C, Chien Y-H, et al. AADC deficiency: occurring in humans, modeled in rodents. Adv Pharmacol. 2013;68:273-284. 14. Pearson TS, Pons R, Ghaoui R, Sue CM. Genetic mimics of cerebral palsy. Mov Disord. 2019;34(5):625-636. doi:10.1002/mds.27655.