Background: Pegvisomant is a growth hormone receptor antagonist approved for the treatment of acromegaly. Documented adverse effects include headache, injection-site reactions, flulike syndrome, and reversible elevation of hepatic enzymes. Skin manifestations at the injection site are reported in similar to 11% of patients and are characterized as erythematous, self-limited reactions that neither require treatment nor lead to drug discontinuation. Objective: This report describes a skin reaction and fever occurring after treatment with pegvisomant in a patient with acromegaly. Case summary: The patient was a 54-year-old white woman with acromegaly (weight, 85 kg; height, 170 cm). At the time of consultation, her medication regimen was levothyroxine 150 mu g/d for hypothyroidism and amlodipine 5 mg/d for hypertension. She started treatment with the somatostatin analogue octreotide acetate 20 mg every 4 weeks, which was then adjusted to 30 mg. Treatment was associated with only partial suppression of insulin-like growth factor-1 concentrations (from 980 ng/mL to 352, 632, and 480 ng/mL at 3, 6, and 9 months, respectively). At this point, octreotide was discontinued and treatment was initiated with pegvisomant 10 mg/d SC. This treatment was initially well tolerated, but after 11 days, she developed an intense erythematous pruriginous reaction at the injection site accompanied by fever (39 degrees C) for 48 hours and, simultaneously, similar lesions at each site of the previous injections. Pegvisomant was discontinued and methylprednisolone 40 mg/d was started, followed by complete disappearance of the lesions in 5 days. Based on the Naranjo algorithm, the adverse reaction observed was probably related to pegvisomant treatment (score = 6). Conclusions: We re who developed a skin reaction and fever probably associated with pegvisomant administration. The reaction subsided 5 days after the drug was discontinued and methylprednisolone treatment was given. (Clin Ther. 2010;32:246-249) (C) 2010 Excerpta Medica Inc.