Diagnosic Dilemma No. 11 


Contributor: Emeritus Professor John Goldsmid, University of Tasmania

 
This diagnostic dilemma relates to two patients in Tasmania .One presented with small, itchy lumps on his arms and the other presented with an itchy rash. In the first case, one of the lumps was excised and sent for histology. A photomicrograph of the findings from the case are given below as Fig 11.1. The finding from a skin scraping from the second case is shown in Fig 11.2:
Image 1
Figs. 11.1 - Organism removed from lesion of Patient 1
Image 2
Figs. 11.2 - Organism from skin scraping of rash from Patient 2

What is your diagnosis?



 


Patient 1

The lump was found to contain a hard bodied organism (Arthropod) identified as a thrips (Insecta: Thysanoptera) from the frilled wings (cf Figs 11.1 and 11.3)

Image 1
Figs. 11.1 - Organism removed from lesion of Patient 1
Image 3
Fig. 11.3 - Part of thrips thorax to show frilled wings (redrawn from Reed, 1973)

Thrip bites are discussed by Alexander (1984) as causing itchy “evanescent pinkish dots” and he records suggestions that thrip bites may result in papular eruptions. He sates that in dry weather, thrips are attracted to moisture, including sweat on human skin but mentions no records of these insects actually invading into the skin as was noted in this case.

Patient 2

: The skin scraping from this patient was found to contain a hard bodied organism (Arthropoda: Insecta) which from the characteristic posterior furcula, could be identified as a collembolan, or springtail (cf Figs 11. 2 and 11.4).

Image 2
Figs. 11.2 - Organism from skin scraping of rash from Patient 2
Image 4
Fig. 11.4: Posterior abdomen of a collembolan to show the furcula (redrawn after Wallace and Mackerras, 1973)

Collembolans have been recorded as being associated with a pruritic dermatitis as discussed by Dasgupta and Dasgupta (1990)

 
References:
Alexander, J. O’D. (1984) Arthropods and Human Skin. Springer-Verlag. Berlin.
Dasgupta, R. and Dasgupta, B. (1990) Collembolan insects as potential parasites. Trans.R.Soc.Trop.Med.: 84: 438.
Reed, E.M. (1973). Thysanoptera. In: The Insects of Australia. CSIRO. Melbourne University Press . P 462.
Wallace, M.M.H. and Mackarras, I.M. (1973) The entognathous hexapods. In: The Insects of Australia. CSIRO. Melbourne University Press p. 210




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