[Late-onset vaccination-induced subcutaneous pseudolymphoma]

Area of Science:

• Immunology
• Dermatopathology
• Vaccinology

Background:

• Aluminium hydroxide is a common adjuvant in vaccines, enhancing immune response.
• Rare adverse reactions, including localized skin reactions, can occur at vaccine injection sites.
• Persistent nodules are an uncommon, delayed presentation following vaccination.

Observation:

• A case of a persistent subcutaneous nodule presenting four years after diphtheria, tetanus, and pertussis vaccination is described.
• The nodule's late onset caused diagnostic uncertainty prior to histological examination.
• Histopathology revealed features consistent with a subcutaneous pseudolymphoma.

Findings:

• The pseudolymphoma was confirmed to be associated with the vaccine injection.
• Aluminium was detected in the paraffin-embedded tissue using Morin staining and atomic absorption spectrometry.
• This confirmed the diagnosis of a vaccination-induced pseudolymphoma.

Implications:

• This case underscores the importance of considering vaccination history in the differential diagnosis of late-onset subcutaneous nodules.
• It highlights a rare but identifiable complication associated with aluminium-containing vaccines.
• Further research may elucidate the mechanisms behind vaccine-induced pseudolymphoma formation.