What is the role of genetic and lab testing in the workup of Kennedy disease (KD)?

Updated: Sep 30, 2019
  • Author: Paul E Barkhaus, MD, FAAN, FAANEM; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Depending on level of suspicion, immediate genetic testing for Kennedy disease (KD) may be performed to confirm the diagnosis, obviating other tests, such as EMG and enzyme studies for hexosaminidase deficiency. The availability of genetic testing markedly expedites the evaluation for KD. [66]

Problems may arise in resolving apparent positive results obtained before genetic testing is done. For instance, serum creatine kinase (CK) testing is not indicated, yet the CK level may be elevated substantially. One of the author's patients had been treated for inflammatory myopathy for years before the correct diagnosis was made. In another case, the patient was aggressively treated for myasthenia gravis (including thymectomy) before KD was diagnosed. [67] Sorenson and Klein have also reported elevation in CK and transaminases levels in asymptomatic patients with KD. [68]

Appropriate initial testing and monitoring is indicated because of associated conditions such as diabetes mellitus, lipid disorders, and other endocrine disorders.

If genetic findings are negative in an individual who has clinical findings suggestive of KD, other laboratory investigations may be indicated (see Table 1, Table 2).


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