What is the likely pathogen in a young patient with unilateral cervical adenopathy presenting with purplish hue and granulomas on biopsy?

The presentation of unilateral cervical adenopathy paired with a purplish hue and granulomas on biopsy strongly suggests an atypical mycobacterial infection, specifically Mycobacterium avium-intracellulare. This organism is a part of the non-tuberculous mycobacteria (NTM) group and is notably associated with cervical lymphadenitis in children. The characteristic granulomatous response upon biopsy aligns with the body's attempt to contain this pathogen, and the purplish hue can be associated with the vascular changes in the affected lymph nodes.

In pediatric patients, particularly, cervical lymphadenitis caused by this pathogen can sometimes mimic more common infections, but the specific combination of symptoms, including the granulomas, steers the diagnosis toward an NTM. While Staphylococcus aureus can cause lymphadenopathy, it typically presents with acute, painful lymphadenitis rather than the chronic and granulomatous presentation seen here. Histoplasma capsulatum is primarily associated with pulmonary and disseminated infections, rather than isolated cervical adenopathy. Escherichia coli, as a common bacterial pathogen, would typically cause different types of infections, not characteristically presenting with the described findings. Overall, the nuances of the clinical presentation and