Post-vaccination subcutaneous aluminum granuloma

Vaccination is a successful and cost-effective public health intervention. Aluminum-containing adjuvants are used worldwide to improve the immune response of vaccines. Side effects of aluminum-containing adjuvants in skin and subcutis are usually accompanied by persistent itch, and it may be challenging to diagnose asymptomatic cases. Here we present a case of a 1-year-old girl with asymptomatic subcutaneous nodules. Magnetic resonance imaging (MRI) revealed subcutaneous lesions: 16 mm on the upper right and 4 mm on the upper left arms. Histological examination revealed a granulomatous reaction with lymphoid follicle-like structures in the subcutis, accompanied by a considerable number of macrophages with PAS-positive granular cytoplasm. Moreover, the granules stained positive with aluminon staining, which revealed the existence of aluminum. These findings indicate post-vaccination aluminum granuloma. Due to the benign nature of aluminum granuloma and the benefit of routine vaccination, we decided to recommend that the patient continue taking the routine vaccination.