Orbital myiasis in neglected orbital retinoblastoma

INTRODUCTION

Orbital myiasis, the infestation of orbital tissues by dipterous larvae, is a rare but serious complication typically associated with poor hygiene, low socioeconomic status, and neglected ocular or periocular conditions. When occurring in the setting of malignancy, such as retinoblastoma, it indicates severe disease progression and is often a sign of prolonged neglect and advanced local invasion. Retinoblastoma, the most common intraocular malignancy in children, can extend beyond the globe into the orbit if left untreated, resulting in a disfiguring and life-threatening clinical picture. The combination of orbital myiasis and retinoblastoma is exceedingly uncommon, with very few cases reported in the literature.

We present a rare and alarming case of orbital myiasis complicating a neglected orbital retinoblastoma in a young child. This report highlights the importance of early diagnosis and intervention in paediatric ocular malignancies, underscores the consequences of socio-economic disparities in healthcare access, and discusses the clinical challenges associated with managing such complex, neglected orbital pathologies.

THE CASE

A pre-school child was brought by her father to the oculoplasty clinic with sudden protrusion of the left eye for 1-week, associated with fever and swelling in the cheek and pre-auricular region. Her parents had noticed a white reflex in her left eye since birth, but no medical attention was sought. She had no light perception in the left eye but could see objects at a distance in the right eye. Fundus details could not be made out in the left eye, while the right eye was within normal limits. Magnetic resonance imaging (MRI) orbits and brain, bone marrow biopsy, cerebrospinal fluid cytology, fine-needle aspiration cytology (FNAC) of the preauricular lymph node, abdominal ultrasound, whole-body bone scan and examination under anaesthesia were done. MRI was suggestive of T1-weighted (T1W)/T2-weighted intermediate signal intensity enhancing lesion involving the entire left globe and T1W hyperintense foci in the supero-temporal quadrant suggestive of calcification probably due to retinoblastoma. Metastatic workup was negative, thereby limiting our diagnosis to stage-IIIb extraocular retinoblastoma.

She received 3 cycles of chemotherapy and was scheduled for exenteration followed by radiation. Four months later, she returned with severe swelling, discharge and bleeding from the left orbit and infestations by maggots (Fig. 1a). There was complete destruction of the globe with necrosis and unidentifiable ocular structures. Immediate mechanical forceps removal of the maggots was done after irrigation with turpentine oil. MRI was done to rule out intracranial extension. The dirty-whitish maggots (larvae), about 12-mm long (around 40), were removed at the first attempt. The wound was cleansed daily, and over the course of the next 3 days, an additional 15 larvae were extracted (Fig. 1b). The larvae were sent for entomological assessment which confirmed these to be of the common house fly (Musca domestica) (Fig. 1c). The patient was treated with systemic antibiotics, oral ivermectin and topical antibiotic drops and ointment. After reduction in inflammation, she was referred to medical oncology for second-line chemotherapy including vincristine, cyclophosphamide, doxorubicin, carboplatin and etoposide followed by orbital exenteration. Histopathology showed all margins were free of tumour, residual viable poorly differentiated cells with occasional rosettes (G3) and areas of dystrophic calcification (Fig. 1d), necro-inflammatory exudate with entrapped parasites (larval form) with body structures (Fig. 1e). She had an episode of varicella during the peri-operative period with good recovery (Fig. 1f).

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Fig 1.

(a) Patient presenting with orbital myiasis after 4 months of defaulting from chemotherapy with severe proptosis and maggot infestation; (b) Scientific name: Musca domestica Linnaeus (Insecta: Diptera: Muscidae) Fly, Common name: House fly; (c) Extracted larvae from the necrosed tissue after irrigating with turpentine oil; (d) Haematoxylin-and-eosin (H and E) stained section (20x magnification) showing residual viable poorly differentiated cells (yellow block arrow) with occasional rosettes (G3; red triangle) and areas of dystrophic calcification (green block arrows); (e) H and E-stained section (2x magnification) showing necro-inflammatory exudate with entrapped parasite (larval form) with body structures (yellow block arrow: body wall of parasite; red triangle: body parts/intestine); (f) Healthy socket following orbital exenteration with scar marks of previous episode of varicella during perioperative period.

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DISCUSSION

Orbital myiasis is caused by larvae of different fly species, M. domestica being an infrequent cause. The primary treatment includes manually removing the immobilized maggots after applying topical chloroform, ether, ethanol, turpentine or hydrogen peroxide. Contributing factors include compromised periorbital tissues due to malignant disease, surgery, ischaemia, infection, crowded living conditions, low socioeconomic status, poor personal hygiene and a large number of insects in the vicinity.^1,2 In this particular patient, the combination of weakened orbital tissues due to metastases and close proximity to a housefly infestation likely led to accidental ophthalmomyiasis. Orbital myiasis in neglected eyelid and orbital malignancies such as squamous cell carcinoma,³ basal cell carcinoma^4,5 and retinoblastoma⁶ have been previously described. Treatment involves mechanical removal of the maggots and surgical debridement of necrosed tissue followed by reconstruction. Only a limited number of cases have been documented where orbital myiasis has progressed to the extent which necessitates exenteration.