Editor,
A 42-year-old South-Asian male presented with multiple new painful lumps in his right groin, 1 week after receiving his 2nd dose of the Pfizer vaccine in the left arm. Systematic questioning did not reveal any history of temperatures, night sweats, or weight loss. There was no history of injury to the right leg or any signs of local infection. There also was no history of genital discharge or ulceration. No past medical history of tuberculosis or family history of cancer was noted. Recent travel history was unremarkable.
On examination two lumps were palpable in the distribution of the vertical chain of inguinal lymph nodes. These were tender, firm in consistency and had a smooth surface. Systemic examination revealed no significant lymphadenopathy in the other regions. Abdominal and urogenital examination was also unremarkable.
Biochemical investigations revealed normal inflammatory markers including white cell count of 5.49 cells109 /L, C-Reactive protein 0.7 mg/L and ESR2 mm/hour on 2 consecutive samples thereby making the suspicion of an infectious aetiology like tuberculosis less likely. Lactate dehydrogenase was 180 U/L and full blood count was normal (Haemoglobin 150 g/L, Platelet count 265 cells 109/L) ruling out the possibility of haematological malignancy. Other biochemical tests including urea and electrolytes, liver enzymes, ferritin, vitamin B12 and folate levels, corrected calcium, and alkaline phosphatase levels were all found to be within normal range. An ultrasound scan (USS) confirmed two inguinal lymph nodes (Figure 1 images a, b) with the largest lymph node measuring 3cm in diameter and described as homogenous with preserved hila in keeping with reactive lymphadenopathy. A follow up USS in 4 weeks revealed a significant reduction in size (6mm) (Figure 1 images c, d) and their appearance was also reported to be normal. Further clinical follow-up in 3 months revealed absence of any ongoing or new symptoms and complete resolution of inguinal lymphadenopathy.
Fig. 1:
Grey scale (a) and Colour Doppler (b) ultrasound images of the right groin 10 days after the COVID vaccine demonstrated a mildly enlarged superficial femoral lymph node (vertical group) measuring 11.4 mm in short axis diameter with preserved fatty hilum and minimally increased hilar vascularity, in keeping with a reactive lymphadenitis, corresponding to clinically palpable mildly tender lump.
Follow up grey scale (c) and Colour Doppler (d) ultrasound images of the right groin showed complete regression of the reactive lymphadenitis to normal, appearing right superficial femoral lymph node measuring 6 mm in short axis diameter with negligible vascularity on colour Doppler correlation.
At the time of writing this report non-regional reactive lymphadenopathy had not been reported as a possible transient side-effect to any vaccine1, 2, 3. This is hence the first reported case in literature highlighting this novel side-effect. The authors acknowledge the absence of a definitive investigation that could confirm direct causation between the vaccine and our case’s presentation. However, the absence of any other plausible explanation, the timing of development of the symptoms after the vaccine administration, and complete clinical and radiological resolution of inguinal lymphadenopathy with conservative management supports the hypothesis that this was an adverse reaction to the novel vaccine. Furthermore, the initial radiological appearance of a reactive lymphadenopathy also reinforces our suspicion.
This case emphasizes the importance of obtaining recent immunization history in people presenting with unexplained lymphadenopathy, thereby possibly avoiding the need for further CT imaging and invasive lymph node biopsy tests. There has also been a lot of interest in investigating the migratory function of dendritic immune cells as a cause of local lymphadenopathy following inflammation4, 5. This case also highlights the need for further research to fully understand the pathophysiology of distant site lymph node activation following vaccine administration.
Footnotes
UMJ is an open access publication of the Ulster Medical Society (http://www.ums.ac.uk).
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