Letters

There have been reports of an increase in the prevalence of urolithiasis in lichen planus (LP) [1, 2]. The present study was carried out in an attempt to evaluate the various lithogenous factors in LP. Seventy-five consecutive patients with LP of all age groups and sexes were recruited from July 1995 to December 1996. The age, sex, duration and associated cutaneous and/or systemic diseases, particularly with reference to the renal system if any, were recorded. Diagnosis was made based on the clinical features and biopsy in atypical cases. Estimation of serum calcium and uric acid and also 24-hour urine analysis for calcium, phosphorus, uric acid, urea and creatinine were done using a sequential multichannel analyser IIC (Technicon, USA) in all patients. An ultrasonogram (USG) of the abdomen was made in all the patients. Sixty-two individuals, group matched for age and sex without known metabolic, malignant or infectious disease and untreated with diuretics, served as control. Both patients and controls were investigated in a similar manner. The statistical analysis was done using Student’s t test. Seventy-five patients with LP included 32 men and 43 women (average age 35.4, range 18–52 years). The average duration of LP was 3.2 months (range 7 days to 2 years). Of the 62 controls there were 25 males and 37 females with an average age of 38.5 years. None of the controls gave any history, past or present of urolithiasis. All the biochemical parameters in the controls were within the normal range. USG studies did not reveal any abnormality either. They had no systemic or cutaneous disease. Nine patients with LP (12%) gave a history of urolithiasis, 6 in the past and 3 at the time of presentation. Six patients were hypertensive and 4 were diabetic. Two patients had had viral hepatitis in the past. None of the patients had any other cutaneous disease of any consequence. The mean serum values of uric acid and calcium as well as 24-hour urinary values of uric acid, phosphorus, creatinine and urea were within normal limits in all the 62 LP patients. However, serum uric acid levels and urinary calcium levels in patients with a history of urolithiasis were elevated significantly as compared to the controls and patients without urolithiasis (p <0.005). The USG revealed renal stones in only 2 of the 9 patients with a history of urolithiasis in the past or at the time of presentation. LP may be associated with multiple systemic diseases and various biochemical abnormalities [3–5]. Urolithiasis has been described in LP and a preliminary report suggests that there is a 6to 12-fold increase in urolithiasis [1]. The overall prevalence of the history of urolithiasis in our series was 12%, which is close to the figure of 15% in a previous report on 130 patients [2]. Consistent with the earlier observation [2], most of our patients (6/9; 67%) had urolithiasis before the onset of skin lesions. The present study revealed the existence of hypercalciuria and hyperuricemia in all patients with a history of urolithiasis. However, Halevy and Feuerman [3] had reported various biochemical abnormalities, i.e. hyperuricemia, hyperuricosuria and hypercalcemia, in 9 of their 42 patients. The exact cause of these metabolic deviations and their possible role in urolithiasis is not known. The very fact that urolithiasis has been present before the onset of LP in all of our patients strongly suggests that it is probably related to a primary intrinsic defect in uric acid metabolism and the calcium metabolism secondary to it.