Myiasis in a Case of Pentazocine-Induced Cutaneous Ulceration: A Double Whammy.

Sir,

A 22-year-old man presented to us with complaints of recurrent painless ulcerations of the upper limbs for the preceding 2 years and a peculiar crawling sensation on the affected areas for the last 2 weeks. He also had malaise and occasional mild fever. Cutaneous examination revealed multiple discrete and coalescent punched-out ulcerations of varying size on the right forearm. Focal black-colored crusting was present on the ulceration.

The margins of the ulcers were undermined at places and appreciable violaceous hue was evident on the margins [Figure 1]. The adjacent skin showed thickening and woody induration. Multiple healed atrophic scars were also noted on both the forearms [Figure 2]. In addition, a few maggots were seen to come out of the ulcers [Figure 3]. The larvae were manually extracted and later identified as Chrysomya bezziana, based on the characteristics of a mature larva and patterns of the anterior and posterior spiracles.

Figure 1

Multiple discrete and coalescing punched-out ulcerations of varying size with focal black eschars. The margins of the ulcers were undermined at places and a violaceous hue was noted

Figure 2

Multiple-healed atrophic scars on the forearm

Figure 3

(a and b): Maggots coming out from the ulcers

Laboratory investigations including complete blood counts, liver and renal function tests, urine examination, chest X-ray, human immunodeficiency virus (HIV) serology, serum (Hepatitis B surface antigen (HBsAg) and antibody to hepatitis C virus (anti-HCV) were noncontributory. Gram stain of the swab taken from the lesion showed gram-positive cocci.

Bacterial culture grew out Staphylococcus aureus which was sensitive to ciprofloxacin. Mycobacterial culture was negative. A skin biopsy specimen from the margin of one of the ulcers showed mild acanthosis, focal spongiosis and nonspecific inflammatory changes in the form of upper-dermal scattered lymphocytic infiltrates. Based on these clinical features, we suspected injectable drug abuse.

Initially he denied any such history and pyoderma gangrenosum, self-induced lesions, cutaneous tuberculosis and atypical mycobacterial lesions were also considered as the differential diagnosis.

However, with a high degree of confidentiality, the patient admitted that he used to take intravenous as well as subcutaneous pentazocine regularly on the affected sites. Psychiatric assessment revealed that from the age of 16 years, he started taking opioids by sniffing and subsequently shifted to injectable formulations (pentazocine) with incremental dosage which he never tried to quit. Since adolescence, he used to be involved in stealing in group and fighting. Neither he had sympathy for anyone nor any remorse for doing wrong things. Based on the clinical features and psychometric assessment, he was diagnosed to be a case of antisocial personality disorder.

He was treated with aseptic dressing for ulcers along with oral ciprofloxacin. Cotton gauze impregnated with turpentine oil was placed over the ulcer for approximately 10 minutes followed by manual removal of the maggots with the help of tissue-holding forceps.

His ulcers showed gradual signs of improvement within a couple of months. He was also given oral substitution with buprenorphine and naltrexone in tapering doses and divalproex sodium along with regular counseling.

The drug 'pentazocine' was introduced in 1967 as a potent 'nonnarcotic, nonaddicting' analgesic. Subsequently, the abuse potential of the drug was recognized and several cutaneous complications of its use or abuse came into light. The most prominent side effect of pentazocine is cutaneous ulcerations.[123] We report here a case of myiasis in a patient with pentazocine-induced cutaneous ulceration; a hitherto unreported association.

There is no gold standard diagnostic investigation for pentazocine-induced ulcers. Histopathological examination of a skin biopsy specimen typically shows nonspecific inflammatory changes. Pentazocine can be detected qualitatively in urine by thin-layer chromatography and quantitatively by gas chromatography or mass spectrometry.[2]

However, a negative result does not rule out pentazocine use. This is in view of the fact that if pentazocine has not been used in the recent past, the results might be negative. Healing can occur with conservative treatment. Nevertheless, surgical excision followed by skin grafting may be necessary for the nonhealing ulcers. Diagnosis of pentazocine-induced ulcers requires a high index of suspicion.[2]

A few indicators of pentazocine-induced cutaneous ulcers have been described by Prasad et al.[1] They include irregular-shaped deep ulcers with black eschars and surrounding induration, halo of hyperpigmentation, ulcers/nodules/scars along superficial veins, woody induration, needle prick marks/thrombophlebitis, puffy hands, difficulty in venous access, fibrous myopathy and apparent indifference of the patient (lack of discomfort). Past history of a chronic painful medical condition, previous iatrogenic administration of pentazocine, and patients related with medical profession (relatively easy access to the drugs) are the additional risk factors.[1]

The pathogenesis of pentazocine-induced skin changes remains elusive. Schlicher et al.[4] hypothesized that the precipitation of acidic pentazocine in the alkaline pH of extracellular fluid was the cause of the inflammatory reaction, whereas Parks et al.[5] suggested that vessel thrombosis subsequent to pentazocine injection may lead to the formation of ulcers.

The acute complication of ulceration may be due to vasoconstriction and steato-necrosis, while the sclerosis seen in chronic cases is the result of extensive dermal inflammation produced by pentazocine. Toxicity and the irritant properties of the drug might also play a role.[6]

On the other hand, the term, “myiasis” refers to the infestation of live human and vertebrate animals with dipterous (two-winged) larvae (maggots) which, at least for a certain period, feed on the host's dead or living tissue, liquid body-substance or ingested food.[7] Cutaneous myiasis is the most frequently encountered clinical variant and can be divided further into three main clinical manifestations: furuncular, creeping (migratory) and wound (traumatic) myiasis.[6] Flies that cause wound myiasis may include screwworm flies such as Cochliomyia hominivorax and Chrysomya bezziana, and Wohlfahrtia magnifica.

Factors predisposing to infestations by myiasis-producing flies include summer season, contact with infested hosts or visit of an area of infested hosts, sleeping outdoors, poor personal hygiene and poor treatment of wounds, homelessness and travel to an endemic area. Wound myiasis has been reported in several unhealthy cutaneous ulcers including carcinomatous ulcer[89] and perigenital ulcerated seborrheic keratosis[10] amongst others.

We have searched the PubMed and Medline database with the search term 'pentazocine', 'ulcer', and 'myiasis'. However, with best of our effort, we could not find out any previous report of myiasis of pentazocine-induced ulceration in the English language literature in these databases.

Pentazocine-induced ulcers are one of the important causes of nonhealing cutaneous ulcers. Wound myiasis may complicate pentazocine-induced ulcer. Proper precaution should be taken when prescribing injectable opioid analgesics, such as pentazocine, as routine painkillers.

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Conflicts of interest

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