Recurrent cellulitis and bacteremia in a patient with Noonan syndrome: A case report

A 28-year old Japanese man with Noonan syndrome (NS) presented to our emergency department with painful erythema of the trunk and lower extremities since the previous day. He had been diagnosed with protein-losing enteropathy (PLE) with intestinal lymphangiectasia at age 25 years, and undergone lymphaticovenular anastomosis (LVA) twice. Three episodes of cellulitis of both lower extremities had occurred in the past 2 years. Extensive cellulitis with sepsis was diagnosed and piperacillin/tazobactam was started, which was de-escalated to ceftriaxone. He was discharged after 13 days of antibiotic therapy. After discharge, low-dose trimethoprimsulfamethoxazole (SMZ-TMP) was started as the primary prophylaxis, but three episodes of cellulitis occurred in the next year and were treated with other antibiotics. NS, an autosomal dominant disease known as a RASopathy, is caused by germline mutations in RAS-MAPK pathway genes. Lymphedema resulting from lymphatic abnormalities is a concomitant manifestation in 20 % of patients with NS, and can be a risk factor for cellulitis. Hypoalbuminemia and hypoglobulinemia associated with PLE facilitate infections such as cellulitis. As a treatment for lymphedema in the extremities, LVA has shown objective and subjective improvements in most patients, and some studies have also reported its efficacy for lymphedema in patients with NS. Targeted molecular therapy with mitogen-activated protein kinase enzyme (MEK) inhibitor is used in treatment of cancers with activation of the RAS/MAPK pathway. MEK inhibitors have recently been tried in patients with RASopathies and severe lymphatic disorders, and can lead to rapid resolution of symptoms.