Chloroquine Retinopathy Caused by Overdosing Based on Ideal Rather Than Actual Body Weight in an Asthenic Woman

This 67 year old woman with systemic lupus erythematosus was placed on chloroquine 250 mg/d. She was 64 inches tall and weighed 105 pounds (asthenic somatotype). Her adjusted daily dose was 5.24 mg/kg/d based on her actual body weight. Using the National Heart Lung and Blood Institute table of ideal body weight based on height, her adjusted daily dose was 3.92 mg/kg/d. Her cumulative dose of chloroquine was 456 gms. She complained of difficulty seeing and paracentral scotomas. Her ophthalmologist told her initially that nothing was wrong but after 5 years of therapy her rheumatologist took her off chloroquine and a second opinion showed chloroquine retinopathy. Her visual acuity was 20/40 right eye, 20/30 left eye. A- A color fundus photograph of the left eye showed a bull-eye lesion of retinal pigment epithelial atrophy. B - A multifocal electroretinogram showed low amplitudes of R1 and R2, but a normal R1/R2 ratio. C - 10-2 visual fields showed an annular dense scotoma. D - SD-OCT showed loss of the inner segment/ outer segment junction and of the retinal pigment epithelium beginning at the white arrows and involving the fovea as well as the parafovea. The right eye showed similar findings. In more advanced cases of chloroquine retinopathy, the R1/R2 ratio can return to normal as the amplitude of R1 falls. Therefore, it is important not to use this index alone in following the mfERG. The R1 and R2 amplitudes were both below the range of normal for the population. This case illustrates that if a woman has an asthenic somatotype and has an actual body weight less than the ideal body weight, then the actual, not the ideal, body weight should be used in the adjusted daily dosage calculation.