Diagnosic Dilemma No. 13 


Contributors: Emeritus Professor John Goldsmid and Dr. Silvana Bettiol, University of Tasmania

 
Introduction:
These three cases involved patients who submitted small insects which they claimed they had found in their beds (Case 1) or on their heads/bodies (Cases 2,3). In all cases they believed the specimens were either parasitic mites (Case 1) or headlice (Cases 1, 2, 3).

Case 1:
On examination of the specimen submitted in Case 1 the insect found is shown in Fig.13.1
Image 1
Fig. 13.1 - Specimen submitted from Case 1

Case 2:
The specimen submitted in case 2 was badly damaged, but the wings of an insect were recognizable and are shown in Figs. 13.2 & 13.3.
Image 2
Figs. 13.2 - Specimen 1 submitted from Case 2
Image 3
Figs. 13.3 - Specimen 2 submitted from Case 2

Case 3:
In case 3, the patient was clearly very distressed by an ongoing belief that she was infested with headlice or scabies mites. She had undergone numerous and repeated treatments at her own instigation (dogsoap; permethrin) or on the advice from a hospital clinic (benzyl benzoate). She had even shaved off all her hair in a desperate effort to rid herself of the perceived infestation. Her main complaint was the feeling of insects crawling over her (formication) and she subsequently developed a rash on her body. The condition had not improved and the hysteria had spread to other members of her family. On request to submit the insects for examination, she could not get anything recognizable as an ectoparasite but she did submit drawings of the “parasite” made using a magnifying glass (Figs. 13.4, 13.5)
Image 4
Fig. 13.4 - Drawing 1 submitted by patient in Case 3
Image 5
Fig. 13.5 - Drawing 2 submitted by patient in Case 3


Were the specimens submitted in cases 1, 2 and 3 the same type of insect?


Were they of any clinical significance in the cases?


What is your diagnosis?



 


The insects submitted in Case 1 (Fig 13.1) were undoubtedly wingless psocids (See Essig, 1954, Smithers, 1973, Goldsmid, 1983).

The specimen submitted in case 2 consisted of crushed insect remnants with only the wings being recognizable. Psocids can exist in both winged and wingless forms ( Essig, 1954; Smithers, 1973). The wing venation when compared to psocid wings illustrated by Smithers (1973) (Fig. 6) suggests that the submitted insects in Case 2 were also psocids.
Image 6
Fig. 13.6 - Wings from Case 2 (left) compared to diagram of psocid wings from Smithers (right - courtesy of Melbourne University Press)

In case 3, the drawings submitted by the patient had similarities with the head and mouthparts of a psocid (Fig. 13.6)
Image 1
Fig. 13.4 Drawings submitted by patient in Case 3
Image 2
Fig. 13.7 - microphotograph of the head of a psocid to show prominent mandibles
Image 2
Fig.13.5 - Drawing submitted by patient in Case 3
Drawings of the “parasite” from Case 3 compared to a microphotograph of the head of a psocid to show prominent mandibles

Discussion:

In Case 1, the insect submitted as ? either a headlouse/parasitic mite, was undoubtedly a psocid or booklouse (Insecta: Psocoptera) which had been mistaken for a headlouse or ectoparasitic mite by the patient who had had problems with biting animal mites infesting his house previously.
In Case 2, again the insects submitted had been mistaken for headlice by the patient and the GP with the diagnosis being based on the clinical history and supposition. The morphology of the wings here also suggests that the submitted insect was a psocid.
In Case 3, the problem seemed more of a case of delusional parasitosis similar to those discussed by Frean (2010) with the submitted drawings again looking like parts of a psocid head - especially the prominent mandible-like structures.

While a definite identification was only possible in one of the three cases, the evidence suggests that psocids were involved in all three cases, not so much as parasites and a cause of symptomatic ill health as for being blamed for the perceived medical problems (physical such as itching or a rash, or psychological) in all 3 three cases. In Case 3, the rash may well have been due to repeated use of various topical remedies applied to the skin.
Overall, psocids are not considered to be of any medical significance, being scavenging insects very common in the environment. However, Smit (1954) describes how psocids, which are often found in huge numbers in houses and in damp roofing material (eg thatch), can “ fall on to the occupants and on everything in the house, causing much consternation. They do not bite human beings but cause some irritation when crawling over the skin”
 
References:
Essig, E.O. (1954) College Entomology. NY MacMillan
Frean, J (2010). Delusional parasitosis: Case series and a review of the literature. Annals of the ACTM. 11.21 - 23
Goldsmid, J.M. (1985) Unusual arthropod ectoparasitic infestations of man. Aust. Fam. Phys. 14: 386-388.
Smit, B. (1964) Insects in Southern Africa: How to Control Them. Oxford University Press. Cape Town
Smithers, C.N. (1973) Psocoptera. In: The Insects of Australia. Canberra. 1973. Melbourne University Press. pp 367-375.



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