Case Presentation: A 70 year-old female with migraines, type 2 diabetes and hypertension presented with progressively worsening headaches, fatigue, fevers, and 20 lb weight loss over six months. She had extensive workup revealing elevated inflammatory markers and an MRI brain three months prior showing a mildly expansile lesion in the right sphenoid bone (Fig. 1A). CT head and bone scan confirmed a lesion in the right sphenoid and clivus. Lumbar puncture showed culture negative CSF pleocytosis (WBC 1918, 73% PMNs). Transsphenoidal biopsy of the sphenoid bone grew Staphylococcus epidermidis and detected Aggregatibacter actinomycetecomitans on broad-range PCR with pathology showing lymphohistioplasmacytic inflammatory infiltrate, necrosis, and foci of actinomyces. The actinomyces and actinomycetecomitans were thought to be contaminants from the sinonasal cavity. The patient was treated for the Staphylococcus epidermidis infection with doxycycline. She reported initial improvement of headaches, but then symptoms and fevers recurred prompting her return to the hospital. Repeat MRI brain showed extensively infiltrative lesions into the sella turcica, clivus, cavernous sinuses, cranial nerves and right orbital apex as well as C1 and the right prevertebral musculature (Fig. 1B). CT neck revealed soft tissue masses within the right infrahyoid neck. MRI total spine showed new leptomeningeal nodules. Repeat lumbar puncture was unchanged. Patient underwent biopsy of two neck masses that both showed actinomyces suppurative lymphadenitis. Given multiple biopsies positive for actinomyces and acute on chronic inflammatory changes, diagnosis was consistent with actinomycosis. The patient was started on treatment with penicillin G.
Discussion: Actinomyces encompasses a group of commensal anaerobic or microaerophilic gram-positive rods that make up the normal flora of oropharynx, skin, gastrointestinal and female genital tracts. They can cause indolent granulomatous infections, most commonly in the cervicofacial, thoracic and abdominopelvic sites, but rarely involve the central nervous system. Concomitant infections with Aggregatibacter actinomycetecomitans, a HACEK gram-negative rod found in the oral cavity, are common. Radiographically and clinically, actinomycosis can mimic malignancy. It’s slow progressing and associated with constitutional symptoms. It appears as mass lesions and can be difficult to discriminate from cystic or necrotic tumors with routine imaging such as CT and even MRI. Prior case reports of CNS actinomyces have mimicked presentations of lymphoma, meningioma, metastatic cancer and chronic granulomatous diseases. Treatment involves prolonged antibiotic courses, usually with penicillin G as the drug of choice. Susceptibilities are rarely tested on anaerobes but most are susceptible to beta lactams. In cases that involve extensive necrotic lesions, surgical debridement is warranted. Prognosis is generally favorable.
Conclusions: Actinomycosis is an uncommon slow progressing granulomatous infection. It can affect both immunocompromised and immunocompetent hosts. Diagnosis can be difficult due to its unusual clinical presentations that often mimic other inflammatory, infiltrative and neoplastic conditions, but it is important to be considered in the differential. Prompt tissue diagnosis is essential for timely treatment.
