Unsuspected invasive neonatal gastrointestinal mucormycosis: A clinicopathological study of six cases from a tertiary care hospital.

AIM: To analyse the clinicopathological features of neonatal mucormycosis
MATERIALS AND METHODS: Retrospective analysis of cases of neonatal gastrointestinal mucormycosis.
RESULTS: THERE WERE SIX NEONATES WITH MALE: female ratio of 1:1. Except one all were preterm babies. The clinical presentation was abdominal distension in the majority. All were clinically diagnosed as either NEC or toxic megacolon with perforation. Neonatal gastrointestinal mucormycosis was not suspected clinically in any. All the children were explored immediately. Biopsy revealed transmural hemorrhagic necrosis/infarction of the intestinal wall with fungal hyphae.
CONCLUSIONS: The physicians should have a high index of suspicion for gastrointestinal tract mucormycosis in neonates with metabolic disturbances who present with abdominal distension and pneumoperitoneum. Early diagnosis and aggressive medical and surgical treatment may improve the outcome of neonates with this potentially lethal invasive disease.

INTRODUCTION

Mucormycosis is an uncommon opportunistic infection caused by fungi belonging to the order Mucorales of the class Zygomycetes. The order includes the genera Absidia, Mucor, Rhizomucor and Rhizopus (Mucoraceae). These fungi are ubiquitous saprophytes of soil and decaying vegetable matter producing large numbers of airborne spores that are the infective form. Infections occur in the rhinocerebral, respiratory, gastrointestinal, or cutaneous regions, depending on whether the spores are inhaled, ingested, or injected.[1] The incidence of necrotizing enterocolitis (NEC) in the premature infant is high and associated with a mortality of 20-40%.[2] Neonatal gastrointestinal mucormycosis is rare and to the best of author's knowledge 23 cases have been published in English literature.[3-18] We present the largest series of gastrointestinal mucormycosis in neonates from our centre.

MATERIALS AND METHODS

This is a retrospective study from January 2003 to December 2011. Thirty cases of neonatal enterocolitis were operated during this period. A total of 6 cases of mucormycosis of the gastrointestinal tract (GIT) in the neonates were diagnosed during this period and all were included in this study. The material comprised of formalin-fixed paraffin embedded tissue blocks and tissue sections. Additional sections of 3-5 micron was cut and stained with Hematoxylin and eosin, Periodic acid Schiff's and Gomori silver methnamine as required.

RESULTS

The clinical findings and operative data are summarised in Table 1. There were six neonates with male: female ratio of 1:1. All except one were preterm babies. The babies were admitted in various other hospitals for a period of one to seventeen days prior to admission at our centre. Patient number two, four, five and six also received broad spectrum antibiotics prior to admission; however complete details were not available. The clinical presentation was abdominal distension in majority of the cases. At our hospital all were clinically diagnosed to either NEC or toxic megacolon due to aganglionosis with perforation. Neonatal gastrointestinal mucormycosis was not suspected clinically in any of the case. All the neonates were explored immediately. Biopsy from the perforation site revealed ulceration along with extensive transmural hemorrhagic necrosis/infarction of the intestinal wall with polymorphonuclear leucocyte infiltration, haemorrhage and thrombosed blood vessels, and numerous broad aseptate to pauciseptate hyaline fungal hyphae displaying branching at right angles suggestive of zygomycosis [Figure 1]. These filaments were also within the lumen of the vessel and also seen infiltrating the vessel wall [Figure 2]. Evidence of vasculitis was noted in foci. Occasional sections show formation of ill-defined epithelioid granulomas. Fungal elements were also noted infiltrating the intestinal wall in many places. Periodic acid schiff (PAS) and Gomori silver methenamine special stains highlighted these fungi and confirmed the diagnosis of invasive zygomycosis. Tissue cultures were not done in any of the cases. All the neonates were started on Inj Amphotericin B. Two babies died and four survived.

Table 1

Clinical and operative details of the six neonates

Figure 1

Low power view displaying trans mural haemorrhagic necrosis of large bowel wall with invasive fungal elements, (H and E, ×100) (Inset: Higher power demonstrating tissue invasion by zygomycosis, H and E, ×200)

Figure 2

Angioinvasion by fungus, (H and E, ×400) (Inset: Arterial wall invasion with vasculitis H and E, ×200)

DISCUSSION

Organisms of class Zygomycetes are filamentous fungi having low intrinsic pathogenicity. However, these fungi can produce fulminant infection in patients with underlying immune compromised conditions like diabetes and ketoacidosis, starvation, immunosuppression, burns, diabetic ketoacidosis, malignancy or organ transplant.[14] Disease can be disseminated or localized to the rhinocerebral area, lungs, gastrointestinal tract or skin. Rarely the disease may affect healthy individuals.[19] Prematurity, malnutrition, neutropenia (lack of phagocytes), acidosis, and corticosteroid therapy are predisposing factors in children.[4] Mucormycosis of the gut in neonates is rare, difficult to recognize, and, hence, usually fatal.[3-18] These cases are usually diagnosed initially as NEC, resulting in delay in specific treatment.

A review of the English language literature found 23 case reports of neonates who were diagnosed as having gastrointestinal mucormycosis.[3-18] The majority of these infants were premature. Five of our neonates were premature. Similar to our cases, clinical diagnosis of the condition has never been made in any of the published literature. In all cases, the organism was identified by histopathological examination. Isolation of the organism by culture was possible in only 6 of the 23 cases and the organisms were found to belong to the genus Rhizopus. We and some other pathologist believe that diagnosis of invasive mucormycosis is possible only by histopathologic examination of a specimen because cultures can only prove mere presence of this ubiquitous organism but not its vascular or mural invasion.[141418] Cultures were not done in our cases.

It has been generally accepted that the likely portal of entry of the organism is the oropharynx or nares, though the source of infection has been confirmed in only a few cases.[12] The risk factors of neonatal mucormycosis are low birth weight (LBW), neonates having immature immune system and fragile skin barriers. These neonates are usually treated in intensive care units and are administered broad-spectrum intravenous antibacterial therapy and corticosteroids that affect healthy gastrointestinal flora. Similar risk factors were identified in our cases. Kesckes et al. hypothesized that the nursing of premature infants in the high ambient humidity (85%) of enclosed incubators may favor the growth of and an increased environmental exposure to Mucoraceae.[15]

It has also been suggested that GIT mucormycosis may be a variant of NEC. The presentation in premature babies in the medical literature was consistent with NEC in most cases, presenting with abdominal distension, and hematochezia or pneumoperitoneum. It is therefore possible that fungal invasion in premature neonates could be secondary to some combination of GIT vascular compromise, mucosal injury or even NEC itself, since devitalized or dead tissue is more prone to fungal invasion. The main features which differentiate GIT mucormycosis from NEC are the absence of pneumatosis intestinalis, wide spread thrombosis of the small vessels of the gut and the poor response to antibiotics. Uniformly, the prognosis is grave with only seven cases in published literature who survived the illness.[7111617] Therefore survival depends upon the extent of disease, whether it is localized or systemic, on the immunological status of the patient, and the virulence of the organism. In the current series four babies survived the illness as clinicians were alerted by the histopathologist within few hours of specimen received. Rapid processing/frozen section of tissue from involved site with prompt reporting leads to better survival in our neonates. At our hospital we have made a policy to suspect gastrointestinal fungal infection in all cases of neonates presenting with intestinal perforation. Since last three years prophylactic antifungals have also been started in our hospital in premature babies.

In childhood gastrointestinal mucormycosis, the stomach is the most commonly involved organ, followed by the colon, small intestine, and oesophagus. In neonates, the colon is predominantly involved, followed by the stomach and ileum, appendix, and extra intestinal involvement in few cases.[56] Although the symptoms are varied and depend on the site affected, nonspecific abdominal pain and distension associated with nausea and vomiting are the most common symptoms. Fever and hematochezia may also occur. Because of these symptoms the patient is often thought to have an intra-abdominal abscess. The definite diagnosis may be made by biopsy of the suspected area during surgery or endoscopy. Currently, the core management of gastrointestinal mucormycosis includes surgical resection or debridement of necrotic tissue and Amphotericin B therapy. Adequate surgical resection reduces the fungal load and the chances of perforation and long-term sequelae like stricture.

Grossly, the lesion caused by gastrointestinal mucormycosis is ulcerating and necrotic. Histological examination shows variable sized, broad, irregularly shaped, and aseptate to pauciseptate hyphae with right-angle branching.[3-18]

To conclude, neonatal gastrointestinal mucormycosis has an aggressive behavior and should be suspected in any preterm neonate with clinical features of NEC, with necrotizing or perforating lesions of unknown cause, particularly involving the colon. The essence of successful management lies in an early diagnosis with the help of frozen sections, followed by the rapid institution of appropriate therapy, which includes drugs like Amphotericin B and adequate surgical resection of the involved intestine.