Narcolepsy in identical twins.

Narcolepsy has been observed in chronic encephalitis, cerebral arteriosclerosis, brain tumour, and following trauma, but when these cases are excluded there remains a group without demonstrable brain pathology. The existence of this idiopathic group has been a controversial subject. Among the more impressive evidence is that suggesting a hereditary factor in idiopathic narcolepsy. To date this evidence has not contained an account of the condition in identical twins, and the existence of such a case is, therefore, reported. The case came to our notice because one of a pair of twins was referred for psychiatric opinion. The patient a man, aged 28, was admitted for full assessment and at the same time the twin brother was investigated. The monozygotic origin of the twins was shown by application of the similarity diagnosis (Stem, 1950). The following criteria of identicality were applied: (1) Striking similarity in general appearance, and (2) essential identity in (a) hair colour, (b) hair texture, (c) hair form, (d) eye colour, (e) skin colour, (f) amount and distribution of body hair, (g) features of nose, lips, chin, and ears, (h) type and proportions of hands and fingers, (i) height and weight. In appearance both were 6 ft. in height, broadly built, black-haired, and sallow-complexioned. The hands and feet were large, and the jaws were overdeveloped giving a rather acromegaloid appearance to the face. The physical similarities were supported by repeated E.E.G. records which showed the basic similarities expected in identical twins. Their father was interviewed for confirmation of family and early history. He was an ex-professional boxer, of good intelligence.