This website is organized and funded by PTC Therapeutics AB Sweden for healthcare professionals residing in the Nordics and BeNeLux region.

AADC deficiency differential diagnosis


Symptoms of aromatic L-amino acid decarboxylase (AADC) deficiency have considerable overlap with those seen in other neurological disorders, which can lead to misdiagnosis. The infographics on this page describe clinical features present in both AADC deficiency and more commonly seen conditions — cerebral palsy, epilepsy, neuromuscular disorders and mitochondrial disorders — alongside important differentiating signs, to help you to make an accurate, timely diagnosis.

Differential diagnosis of AADC deficiency: Cerebral palsy

Cerebral palsy (CP) is a group of permanent neuromotor disorders causing activity limitation that are attributed to non-progressive disturbances that occur in infancy or early childhood, accompanied by developmental delay.1,2 It is the most common physical disability in children, with a prevalence of 1.7–3.1 cases per 1,000 in high-income countries.3

There are several forms of CP, classified according to which part of the central nervous system is damaged and the different manifestations:4,5

  • Spastic CP is the most common form of the disorder,
    occurring in >70% of cases. Symptoms include stiff, spastic muscles, abnormal movements, difficulties controlling and coordinating muscle movements, impairment of oral, lingual, and palatal movement, resulting in dysarthria and dysphagia. Consequently, failure to reach normal milestones for sitting, crawling and walking results.4,5
  • Athetoid or dyskinetic CP occurs in ~20% of cases and is characterised by slow, writhing movements (athetosis), repetitive, twisting motions (dystonia), and unpredictable, irregular movements (chorea) that can all range from slow to rapid and can be accompanied by pain. Movements may increase with emotional tension and can disappear during sleep.4,5
  • Ataxic CP occurs in less than 5% of cases.
    Symptoms include weakness, poor coordination, tremors and shaky movements, unsteady balance, and difficulty with rapid or fine movement.4,5
  • Mixed CP is a common occurrence whereby patients present
    with a combination of symptoms, but generally it includes spasticity and athetosis.4,5

Many of the childhood manifestations of CP are similar to those seen in patients with a monoamine neurotransmitter disorder such as AADC deficiency, often leading to a misdiagnosis of CP.6 Consequentially, the term “CP mimic” is used to describe a number of neurogenetic disorders that manifest similarly in early childhood.2

Key distinguishing clinical symptoms of AADC deficiency that are atypical in CP
are oculogyric crises and diurnal variation of motor symptoms. Appropriate investigations, including analysis of neurotransmitters in cerebrospinal fluid, are essential for an accurate clinical diagnosis.2,7

CP mimics also show several features that differ from classic CP and can serve as diagnostic clues, including multiple features of autonomic dysfunction. Features of autonomic dysfunction include excessive sweating (diaphoresis), temperature instability, profuse nasal and oropharyngeal secretions, poor gut movements (gastrointestinal dysmotility) and sleep disturbances.2

Brain MRI is a first‐line investigation in a child or adult with an undiagnosed motor disorder which suggests CP. Brain imaging can readily reveal a cerebral malformation as the main cause of neurological symptoms. Aside from cerebral malformation, brain imaging can reveal either normal findings or specific lesions which are characteristic of a genetic disorder or group of disorders, which should prompt further investigation.2

Overlapping and differentiating symptoms of CP and AADC deficiency*

Comparison between CP and AADC deficiency

*Not an exhaustive listSeizures are relatively uncommon in CP, and uncommon in AADC deficiency, but have been reported in both. Seizures in CP have been reported primarily to be of a generalised or partial subtype.12,13Diurnal variation is not always a feature of AADC deficiency but is consistently reported.11


  1. Novak I, et al. JAMA Pediatrician. 2017; 171: 897–907.
  2. Pearson TS, et al. Mov Disord. 2019; 34: 625–636.
  3. Monbaliu E, et al. Lancet Neurol. 2017; 16: 741–749.
  4. Cerebral Palsy Guidance. Cerebral Palsy Symptoms. Available from: Accessed February 2021.
  5. Cerebral Palsy (CP) Syndromes. (n.d.). Merck Manuals Professional Edition. Available from: Accessed February 2021.
  6. Ng J, et al. Nat Rev Neurol. 2015;11:567–584.
  7. Kurian MA, et al. Lancet Neurol. 2011;10:721–733.
  8. Hallman-Cooper JL, Gossman W. StatPearls. Treasure Island, FL: StatPearls Publishing; 2019. Available at: Updated July 18, 2019. Accessed February 2021.
  9. Zouvelou V, et al. Eur J Paediatr Neurol. 2019; 29 (3): 427–437.
  10. Manegold C, et al. J Inherit Metab Dis. 2009;32:371–380.
  11. Wassenberg T, et al. Orphanet J Rare Dis. 2017;12:12.
  12. Gururaj AK, et al. Seizure 2003;12:110–114.
  13. Singhi P, et al. J Child Neurol. 2003;18:174–179.


Explore interactive clinical case studies

Suspect AADC deficiency? Act now

• Tests to diagnose patients with AADC deficiency often show elevated plasma 3-OMD levels1–3

• Earlier diagnosis may be achieved by dry blood spot testing for 3-OMD4,5

Find out more about 3–OMD testing now at:

  1. Wassenberg T, et al. Orphanet J Rare Dis. 2017;12:12.
  2. Chen PW, et al. Clin Chim Acta. 2014;431:19–22.
  3. Brennenstuhl H, et al. J Inherit Metab Dis. 2020;43:602–610.
  4. Hyland K, Reott M. Pediatr Neurol. 2020;106:38–42.
  5. Chien YH, et al. Mol Genet Metab. 2016;118:259–263.


SE-AADC-0303 | April 2024

Welcome to AADC Awareness

A website for healthcare professionals, provided by PTC Therapeutics

This educational website provides information to support the early and accurate diagnosis of rare neurotransmitter disorders, including AADC deficiency

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