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A67-year-oldman receiving rituximab formembranous nephropathy was admitted to the hospital with volume overload. On initial physical examination,a large,nonblanchable, reticulated,hyperpigmented,graybrownpatchwas observed on the patient’s mid and lower back (Figure). He had no pain,pruritus,ordiscomfortonthispatch.He stated that his sister first noticed this patch severalmonths prior to admission. On further questioning, he acknowledged using heating pads frequently for the past 40 years to relieve chronic back pain he has experienced since amotor vehicle crash in 1975. He denies any history of burns or thermal trauma as a result of heating pad use. Quiz at jama.com Figure.Hyperpigmented cutaneous eruption onmid and lower back of patient.

Any new information bearing on the etiology of urolithiasis is important. The composition of calculi has been extensively studied to help clarify the mechanisms of their formation and growth. About 99% of all renal stones are constituted by only four substances, viz., calcium oxalate, apatite, triple phosphate, and uric acid. To the rare types of stones such as xanthine and cystine, a new type can now be added, a calculus composed of pure silicon dioxide. Report of a Case On Jan. 21, 1959, a 53-year-old physician was seen because of severe renal colic. He had had pain for 18 hours, which was not markedly alleviated by 50 mg. of meperidine hydrochloride, hot baths, and a heating pad. Roentgenograms were taken immediately, and a flat plate of the abdomen showed three questionable shadows of "calcific density." Intravenous urography showed prompt and normal visualization of the right kidney but delayed filling of