How does actinomycosis present?

Clinical Presentation of Actinomycosis

Actinomycosis typically presents as a chronic, slowly progressive infection that forms mass-like lesions with characteristic "sulfur granules" and frequently mimics malignancy, most commonly affecting the cervicofacial region (50-60% of cases) following dental procedures or trauma. 1, 2

Primary Clinical Forms

Cervicofacial Actinomycosis (Most Common)

• Develops following dental infections, oral trauma, or procedures in patients with poor oral hygiene 1, 2
• Presents as a painless or minimally painful, indurated swelling in the jaw or neck region 1
• Characteristic "lumpy jaw" appearance with firm, woody masses 2
• May develop draining sinus tracts with discharge containing yellowish "sulfur granules" 1, 2
• Skin overlying the mass often becomes violaceous or reddish-brown 2

Thoracic/Pulmonary Actinomycosis

• Occurs predominantly in smokers with poor dental hygiene 1
• Presents with chronic cough, chest pain, weight loss, and low-grade fever 1
• Frequently mimics lung cancer or tuberculosis on imaging 3
• May show consolidation, cavitation, or mass lesions that cross tissue planes 3
• Can extend through the chest wall creating draining sinuses 3

Abdominal/Pelvic Actinomycosis

• In women, strongly associated with prolonged intrauterine device (IUD) use (>5 years) 1, 2
• Presents as abdominal pain, palpable mass, weight loss, and fever 1, 4
• Commonly mistaken for malignancy, inflammatory bowel disease, or appendicitis 4, 2
• Can involve any abdominal organ; pancreatic involvement is extremely rare 4
• May present with bowel obstruction or fistula formation 2

Cutaneous Actinomycosis

• Occurs after direct inoculation through trauma or in immunocompromised patients 5
• Presents as nodular, indurated lesions that may ulcerate 5
• Can develop draining sinuses with purulent discharge 5
• In immunosuppressed patients (e.g., SLE on immunosuppressive therapy), lesions may be larger and more persistent 5

Key Diagnostic Features

Pathognomonic Findings

• "Sulfur granules" (yellow granules 1-2mm in size) in discharge or tissue, though these are helpful but not specific to actinomycosis 1, 2
• Microscopy shows necrosis with filamentous Gram-positive bacteria arranged in fungal-like branching patterns 1
• Granulomatous inflammatory fibrosis surrounding bacterial nidus 4

Clinical Characteristics

• Chronic, indolent course over weeks to months 1, 6
• Crosses anatomical boundaries and tissue planes (unlike most infections) 2
• Minimal systemic symptoms despite extensive local disease 1
• Mass-like presentation that mimics malignancy is the most common diagnostic pitfall 1, 4, 2

Important Clinical Caveats

The diagnosis is frequently delayed because actinomycosis mimics cancer, tuberculosis, or other chronic infections 1, 2. Many patients undergo surgical resection for presumed malignancy before the correct diagnosis is established 4, 2.

Prolonged anaerobic bacterial cultures (>7-14 days) are essential for diagnosis, as routine cultures often miss the organism 1, 6, 2. Specimens must be transported immediately and cultured under strict anaerobic conditions 2.

In immunocompromised patients, particularly those with SLE or other conditions requiring immunosuppressive therapy, cutaneous lesions may be more extensive and prone to recurrence despite appropriate antibiotic therapy 5.