A 59-year-old woman presents with right-sided, nonradiating, “aching” chest pain that has been continuous and increasing in severity for the past 3 days. It began as a tightness that gradually became more painful; it is aggravated by palpation and movement and has not been relieved by acetaminophen. She has also noted swelling in her right breast and a change in its contour. She reports fevers and chills but denies trauma, shortness of breath, cough, sputum, palpitations, nausea, vomiting, and dysuria.
The patient has diabetes, which was diagnosed 10 years earlier and remains inadequately controlled despite a regimen that includes both long-acting and rapidacting insulin. She has hypertension that has been treated with an angiotensin-converting enzyme inhibitor, a calcium channel blocker, and a diuretic. In addition, she has hepatitis C that has not been treated. She reports no history of chest pain.
This overweight woman has a low-grade fever (temperature, 37.9ºC [100.2ºF]); blood pressure is 155/92 mm Hg. Other vital signs are normal. Pulse is regular, heart sounds are normal, and lungs are clear. The right breast is asymmetrically enlarged, erythematous, warm, and exquisitely tender to palpation. No discrete masses or areas of fluctuance are appreciated. There is no nipple discharge, induration, or axillary lymphadenopathy. She is unable to adduct her right arm because of pain. Results of the remainder of the physical examination are unremarkable.
LABORATORY AND IMAGING STUDIES
Results of a basic metabolic panel are normal except for a blood glucose level of 228 mg/dL. White blood cell count is elevated at 12,900/μL, with 80% polymorphonuclear leukocytes and 2% band forms. Creatine kinase level is 226 U/L. Ultrasonography of the breast shows diffuse edema of the upper outer quadrant of the right breast without evidence of breast abscess. Chest CT scan with contrast and T2-weighted MRI scan of the right pectoralis musculature are shown.
Which of the following is the most likely diagnosis?
A. Diabetic muscle infarction.
B. Spontaneous gangrenous myositis.
C. Cellulitis with skin abscess.
D. Primary pyomyositis.
(answer on next page)