Forty otherwise healthy patients over 50 years of age with early, severe painful herpes zoster were randomly allocated to two groups for treatment. Twenty patients received prednisolone 40 mg daily with gradual reduction over a period of 4 weeks, whilst the other twenty patients received carbamazepine 100 mg four times daily. Thirteen of the twenty patients (65%) in the carbamazepine treated group developed post-herpetic neuralgia lasting up to 2 years, whilst only three of the twenty prednisolone treated patients (15%) had post-herpetic neuralgia lasting up to 6 months only. Thus the incidence and duration of post-herpetic neuralgia were considerably redudced in the prednisolone treated group. In neither group did disseminated zoster or other complications occur.

One hundred patients with 161 positive patch test reactions to a nximber of common allergic sensitizers were re-examined after a period of 10 years, using the same patch test technique. Out of 161 positive patch test reactions, ninety-four (59%) remained positive, forty-four (27%) had diminished reactivity and twenty-two (14%) had become negative.There have been few reports on the persistence of allergic contact sensitivity in the literature which is surprising considering the amount of new knowledge accumulated over the past 50 years in the field of contact dermititis. Table i summarizes the findings of previous investigators. Early investigators thought that epidermal hypersensitivity, once acquired, would persist indefinitely. Ukrainczyk (1932) followed up fifteen patients with skin tests for up to 4 years and found no diminution of hypersensitivity, despite avoidance of the offensive agents. Gomez-Orbaneja & Barrientos (1938), on re-examination of 106 patients after 1-35 years, found that if the offensive agent was removed, the hypersensitivity subsided, or disappeared completely in a large proportion of cases. Bonnevie (1939), however, followed up twenty cases with repeated patch tests for several years without finding any reduction in their hypersensitivity. Thus started a controversy which is still with us today. MATERIALS AND METHODSFrom 1967 to 1970, 863 patients were patch tested at the Department of Dermatology at Hull Royal Infirmary. Of these, 364 gave positive reactions to one or more of the test substances. In 1980 letters were written asking them to attend for re-patch testing. 100 patients (161 positive reactions) complied with the request and were subsequently re-patch tested (a compliance rate of about 27%).In this investigation all patch tests used were closed ones. Results were read 48 h after the

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42 year old woman presented with ischaemic left leg pain. There had been a right above knee amputation two years previously when Buerger's disease was diagnosed. However, on review of the arteriogram there was proximal disease in the superficial femoral artery suggesting atherosclerotic disease, and typical arteriographic features of Buerger's disease were absent. She had been a smoker of 30 cigarettes per day since age 16 years. At presentation two years after the right above knee amputation, the posterior tibial and dorsalis pedis pulses were absent in the left foot but there were no ischaemic ulcers in the toes. The following investigations were normal or negative: fasting blood sugar, lipid profile, C reactive protein, antinuclear antibody, rheumatoid factor, complement, anticentromere antibody, anti-Scl-70, anticardiolipin antibody, and thrombophilia screen. An echocardiogram was also normal. Serum homocysteine was 117.9 µmol/l (5.5-13.6), serum methionine was 16 µmol/l (22-32), serum folic acid was 3.5 ng/ml (3.2-12.4), serum vitamin B12 was 225 pg/ml (158-1050), and serum vitamin B6 was 45 nmol/l (15-73). Genetic testing revealed the patient was homozygous (TT) for the C677T polymorphism of methylenetetrahydrofolate (MTHFR). QUESTIONS (1) Which conditions should be excluded before making a diagnosis of Buerger's disease? (2) What are the causes of a raised serum homocysteine? (3) What is the appropriate treatment for this patient?