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Cataplexy in the Prader–Willi syndrome
  1. E S Tobias1,
  2. J L Tolmie1,
  3. J B P Stephenson2
  1. 1Duncan Guthrie Institute of Medical Genetics, Yorkhill Hospitals, Glasgow G3 8SJ, UK; gbcv55{at}udcf.gla.ac.uk
  2. 2Fraser of Allander Neurosciences Unit, Royal Hospital for Sick Children, Yorkhill, Glasgow G3 8SJ, UK

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We report cataplexy, sudden atonic episodes provoked by emotion, in three patients with Prader–Willi syndrome (PWS) and suggest that cataplexy may be relatively common in this condition.

Detailed questioning of the mother of an 18 year old woman who had PWS elicited a history of recurrent attacks, apparently induced by laughter, with sudden loss of power in all the patient's limbs. If standing, she would slump to the floor but recover completely after a few seconds. She had no history of the sleep paralysis or hypnagogic hallucinations and there was no family history of cataplexy, narcolepsy, or epilepsy. Her EEG was unremarkable. Episodes of cataplexy and of narcolepsy, despite excellent weight control, have been reported by two other patients with PWS who attend this hospital, an 8 year old girl and a 10 year old boy. Only one of the three patients possesses the HLA DR15 (DR2) DQB1*0602 haplotype that is strongly associated with the narcolepsy–cataplexy syndrome.

Cataplexy is usually precipitated by emotion provoking laughter, anger, or joy. The affected individual often falls to the ground without losing consciousness and the phenomenon is often mistaken for an epileptic or cardiac event.1 It can occur in isolation as a dominantly inherited trait or in association with a number of other conditions (table 1). The association between PWS and cataplexy, though described previously,1–5 is not widely recognised. Suspected episodes of cataplexy have been reported in eight of 35,1 four of 25,2 and three of 173 patients with PWS. However, cataplectic manifestations are often “difficult to prove”,1 requiring a detailed history5 that is perhaps seldom available or elicited. We suggest that cataplexy may be relatively common in PWS and enquiries regarding its signs should always be made, especially in any patient with a past diagnosis of paroxysmal events.

Table 1

Conditions in which cataplexy is a recognised feature

References

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