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Photo Quiz: Asteroid bodies in a skin biopsy of a farmer

Summary

A farmer developed nodular skin lesions two weeks after a wrist injury during farming activities, which turned out to be sporotrichosis, a fungal infection caused by Sporothrix globosa. Skin biopsy revealed characteristic structures called asteroid bodies that helped suggest the diagnosis. The infection was confirmed through fungal culture and DNA testing, and was successfully treated with potassium iodide over six months.

Background

Sporotrichosis is a subcutaneous mycosis caused by dimorphic fungi of the genus Sporothrix. The disease can be transmitted through saprophytic contact or animal contact depending on the species involved. Histopathological examination may reveal characteristic asteroid bodies (ABs) formed by yeast cells surrounded by antigen-antibody precipitation complexes.

Objective

To describe a clinical case of lymphocutaneous sporotrichosis in a farmer and discuss the histopathological findings, particularly asteroid bodies, in the diagnosis of this fungal infection.

Results

Fungal cultures yielded Sporothrix globosa confirmed by DNA sequencing. Histopathological examination revealed granulomatous and pyogenic reactions with multiple asteroid bodies containing central yeast cells. The patient achieved complete lesion resolution following a 6-month course of systemic 10% potassium iodide therapy.

Conclusion

Asteroid bodies are useful histopathological clues for diagnosing sporotrichosis when found with central yeast cells, although they are not pathognomonic for the disease. Fungal culture and DNA sequencing remain essential for definitive diagnosis, and potassium iodide remains an effective and affordable treatment option for cutaneous sporotrichosis.
  • Published in:Journal of Clinical Microbiology,
  • Study Type:Case Report,
  • Source: PMID: 40631937, DOI: 10.1128/jcm.00478-25
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