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Differential diagnosis of AADC deficiency

Introduction

The signs and symptoms of aromatic L-amino acid decarboxylase (AADC) deficiency have considerable overlap with those seen in other neurological disorders; diagnosis can be challenging as a result.

Click on the links below to get more information on the clinical features present in both AADC deficiency and more commonly seen conditions — cerebral palsy, epilepsy, neuromuscular disorders and mitochondrial disorders — alongside some important differentiating signs, to help you to make an accurate, timely diagnosis.

Differential diagnosis: Cerebral palsy

Cerebral palsy (CP) refers to a group of permanent neuromuscular disorders of the development of movement and posture causing activity limitation. These disorders are attributed to non-progressive neurological abnormalities that occur in infancy or early childhood.1,2

Many of the childhood manifestations of CP are similar to those seen in patients with a monoamine neurotransmitter disorder such as AADC deficiency.3

Differential diagnosis: Epilepsy

Epilepsy is a chronic neurological disorder characterised by recurrent seizures due to abnormal, excessive or synchronous neuronal activity in the brain.4,5

Paroxysmal events such as oculogyric crises, tonic or dystonic posturing of the limbs, myoclonus and chorea, that are often seen in patients with AADC deficiency, can mimic epileptic seizures and can consequently be mistaken for epileptic seizures.6–10

Differential diagnosis: Mitochondrial disorders

Mitochondrial disorders are a clinically heterogeneous group of disorders that arise as a result of dysfunction of the mitochondrial respiratory chain.11

In infants, clinical features such as hypokinetic rigid syndrome and generalised dystonia can mimic those seen in primary neurotransmitter disorders (such as AADC deficiency), making diagnosis difficult based on clinical presentation alone.12,13

Differential diagnosis: Neuromuscular disorders

Neuromuscular disorders are a broad group of genetic heterogeneous diseases that impair muscle function and/or the peripheral nervous system.14–16

The majority of AADC deficiency patients present with movement disorders (hypokinesia, chorea, dystonia, ballismus, dyskinesia, tremor, myoclonus). AADC deficiency can have a similar presentation to many neuromuscular disorders, such as congenital myasthenia gravis.3,17,18

AADC, aromatic L-amino acid decarboxylase; CP, cerebral palsy.
 
    1. Novak I, et al. JAMA Pediatrician. 2017;171:897–907.
    2. Pearson TS, et al. Mov Disord. 2019;34:625–636.
    3. Ng J, et al. Nat Rev Neurol. 2015;11:567–584.
    4. Fischer RS, et al. Epilepsia. 2017;58(4):520–530.
    5. World Health Organization. Epilepsy: a public health imperative. 2019. Available from: https://www.who.int/mental_health/neurology/epilepsy/report_2019/en/. Accessed April 2022.
    6. Ito S, et al. Dev Med Child Neurol. 2008;50:876–878.
    7. Wassenberg T, et al. Orphanet J Rare Dis. 2017;12:12.
    8. Pons R, et al. Neurology. 2004;62:1058–1065.
    9. Brun L, et al. Neurology. 2010;75:64–71.
    10. Lee WT. Epilepsy & Seizure. 2010;3:147–153.
    11. Adam MP, Ardinger HH, Pagon RA, et al (Editors). GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle;1993–2020.
    12. Marecos C, Ng J, Kurian MA. J Inherit Metab Dis. 2014;37:619–626.
    13. Brennenstuhl H, et al. Neuropediatrics. 2019;50:2–14.
    14. Dowling JJ, et al. Am J Med Genet A. 2018;176:804–841.
    15. van Putten M, et al. Dis Model Mech. 2020;13:dmm044370.
    16. Mary P, Servais L, Vialle R. Orthop Traumatol Surg Res. 2018;104:S89–S95.
    17. Kurian MA, Dale RC. Continuum (Minneap Minn). 2016;22(4):1159–1185.
    18. Pearson TS, et al. J Inherit Metab Dis. 2020;43:1121–1130.

 

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GL-AADC-1025 | April 2022

Welcome to AADC Insights

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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