Thinking Outside the Checkbox

The initial diagnostic branch point for nontraumatic oral ulcers is infectious versus noninfectious. Infections that cause oral ulcers include HSV, CMV, and syphilis. The appearance and occurrence of the ulcers on freely moveable mucosa are consistent with aphthous stomatitis. Recurrent aphthous ulcers may occur in autoimmune diseases, including Behçet disease, Crohn disease, celiac sprue, and reactive arthritis. An endoscopy should be considered to detect esophageal ulcerations or esophageal candidiasis.

The rash may indicate folliculitis, usually attributable to Staphylococcus aureus or to Pseudomonas in the setting of recreational water exposure. Broad-spectrum antibiotics or immunodeficiency predisposes to candida folliculitis, while systemic candidiasis may cause metastatic skin lesions. The most common cutaneous manifestation of Behçet disease is erythema nodosum, but follicular and papulopustular lesions are also characteristic.

Pulmonary nodules are caused by infections, noninfectious inflammation, and malignancy. Infectious causes of pulmonary nodules include septic emboli, bacterial abscesses, and mycobacterial and fungal infection; noninfectious inflammatory causes include vasculitis (eg, granulomatosis with polyangiitis), rheumatoid arthritis, sarcoidosis, and lymphomatoid granulomatosis. Although additional culture data, serologic testing, and tuberculin skin testing or an interferon-gamma release assay may help to exclude these infections, the chronicity of symptoms, and lack of response to multiple antibiotic courses favor a noninfectious etiology.

Thickening of the aorta and left pulmonary artery may arise from an infectious, infiltrative, or inflammatory process. Arterial infections arise from direct inoculation, such as catheterization, trauma, or a contiguous site of infection, or from embolic seeding of atherosclerotic plaques or aneurysms. Malignant and nonmalignant processes, including sarcomas, lymphomas, histiocytoses (eg, Erdheim–Chester disease), and IgG4-related disease, may infiltrate the vascular walls. He has no evidence of visceral organ involvement to suggest these multisystem diagnoses.

The combined involvement of the aorta and pulmonary artery suggest a large-vessel vasculitis. Giant cell arteritis is exceedingly rare in patients younger than 50. Takayasu arteritis is a large-vessel vasculitis that predominantly affects women and may present with hypertension, arterial bruits, or discrepant blood pressure between arms, none of which were reported in this case. Behçet disease affects blood vessels of all sizes, including the aorta and pulmonary vasculature. His fevers, oral ulcers, perifollicular rash, and lymphadenopathy are consistent with this diagnosis, although he lacks the genital ulcers that occur in the majority of patients. Pulmonary nodules in Behçet disease arise from pulmonary or pleural vasculitis, resulting in focal inflammation, hemorrhage, or infarction. An ophthalmologic examination for uveitis and a pathergy test would support this diagnosis.

FDG accumulation in the aorta and pulmonary arteries signals large-vessel inflammation. The lack of FDG-avidity of the ground-glass opacities and nodular lesion suggests that these are not metabolically active tumors or infections but may be sequelae of the underlying disease, such as a hemorrhage or infarction from vasculitis. Sarcoidosis could account for the lung findings, but large-vessel vasculopathy would be exceedingly uncommon. Microscopic polyangiitis and granulomatosis with polyangiitis also cause pulmonary and vascular inflammation, but the nonreactive ANCA, absence of sinus disease, and normal urinalysis and kidney function make pauci-immune vasculitis unlikely. While the large-vessel involvement is consistent with Takayasu arteritis, the oral ulcers and rash are not.