Sir,

We report a 64-year-old insulin-dependent diabetic Caucasian male, on treatment with Dapsone for Dermatitis Herpetiformis, who presented with symptoms of haemolytic anaemia and right anterior ischaemic optic neuropathy (AION). To our knowledge, this is the first report of AION with Dapsone.

Case report

A 64-year-old male insulin-dependent diabetic with Dermatitis Herpetiformis was treated with 100 mg Dapsone daily. The patient was diabetic for 13 years, normotensive, and a nonsmoker.

After 1 month, while on 75 mg of Aspirin, he developed decreased vision on the right eye associated with a headache and shortness of breath.

At initial presentation to another Unit, and having stopped his Dapsone treatment on his own, he had vision of 6/12 (right) and 6/9 (left), no relative afferent pupillary defect, and right optic disc swelling with flame-shaped haemorrhages. A diagnosis of nonarteritic AION (NAION) was made (ESR 12 mm/h). He was then told that Dapsone was unrelated to his condition and restarted his course. After 10 days, he was referred to us with deterioration of vision to counting fingers on the right. He had stopped his Dapsone as he felt that it had made his vision worse again.

At the same time, he described breathlessness and tachycardia. Fundoscopy revealed a swollen disc on the right. Both discs were crowded with 1.9 mm vertical diameter. Humphrey visual fields showed a generalised reduction of sensitivity on the right eye with an altitudinal defect (Figure 1). Blood tests revealed normocytic anaemia with a haemoglobin of 12.9 g/dl (normal range 13.5–18 g/dl), reticulocyte count 125 × 109 (normal range 10–100 × 109), bilirubin of 24 μmol/l (normal range 1–17 μmol/l).

Figure 1
figure 1

Inferior altitudinal field defect on the patient's right eye.

Fluorescein angiography showed late staining of the disc. Autoantibodies tests were negative and Doppler scan of the carotids did not show any obstruction.

After 1 month, visual acuity was still counting fingers on the right with established optic disc atrophy.

Comment

Recognised risk factors for NAION include diabetes mellitus, hypertension, hypercholesterolaemia, collagen vascular disease, coagulopathy, and blood hyperviscosity. The aetiology is believed to be reduced perfusion and oxygenation in the area of the optic nerve head.

Dapsone may cause haemolysis and agranulocytosis, more frequently in patients with Dermatitis Herpetiformis due to immune hyper-responsiveness1 (Table 1), optic atrophy without evidence of optic neuritis, motor neuropathy without haemolysis,2 and macular infarction.3, 4 Dapsone is not thought to cause direct retinal damage at therapeutic levels.5

Table 1 Dapsone side effects

In our case, haemolysis caused by Dapsone in conjunction with insulin-dependent diabetes mellitus, which also affects the functionality of red cells and blood vessels, were likely to be responsible for delayed blood flow and decreased oxygenation of the optic nerve head. This caused the NAION despite administration of 75 mg of Aspirin.

In dermatitis herpetiformis where life-long treatment has to be administered, the risk for ischaemic optic neuropathy should be taken into account, especially in older patients where the prevalence of the risk factors for NAION is increased.