Failure to thrive (FTT) in infants represents a significant clinical challenge requiring comprehensive evaluation to identify underlying causes, which may range from inadequate nutritional intake to systemic disease or environmental exposures. When accompanied by respiratory symptoms and unusual radiological findings, the diagnostic complexity increases substantially. Mercury poisoning, though relatively uncommon in infants, presents with multisystem manifestations that can mimic various conditions, making early recognition critical for appropriate intervention1. Mercury exposure in pediatric populations can occur through various routes including inhalation, which carries significant risk

for chemical pneumonitis and subsequent systemic absorption. The clinical presentation often includes respiratory symptoms, poor weight gain, and neurological manifestations depending on the duration and level of exposure.

This case report describes a term male infant who presented with failure to thrive and was subsequently found to have mercury poisoning, pneumonia, and anemia. The discovery of radiographic artifacts on chest imaging played a crucial role in diagnosis and guided the therapeutic approach. This report aims to highlight the importance of considering environmental toxin exposure in the differential diagnosis of infants with failure to thrive and respiratory symptoms, particularly when accompanied by unusual radiological findings.

PATIENT INFORMATION

Baby of Noushin, a male infant born at term (37 weeks) via lower segment cesarean section (LSCS) due to previous cesarean delivery, had a birth weight of 2300 grams, categorizing him as small for gestational age (SGA). The infant was born to a 20-year-old G2P2L1 mother with third-degree consanguinity in the marriage. The pregnancy was uncomplicated with no history of gestational diabetes mellitus, allergies, hypothyroidism, or pregnancy-induced hypertension. The mother's blood group was AB positive while the baby's was A positive.

The infant cried immediately after birth with no reported complications during the immediate postnatal period. However, by day 70 of life, the baby had failed to gain adequate weight, with his weight remaining approximately the same as his birth weight, prompting referral to the neonatal intensive care unit (NICU) at Paramitha Hospital, Madeenaguda for further evaluation and management1. The family history revealed the first child to be a female who was reported as alive and healthy. There was no history of polyuria, suck-rest-suck cycle, loose stools, or vomiting reported prior to admission.

PHYSICAL EXAMINATION:

At the time of the initial admission, the infant maintained oxygen saturation in room air with vital signs showing a heart rate of 142 beats per minute and a respiratory rate of 50 breaths per minute. Physical examination revealed loose skin folds over the buttocks, loss of buccal pad of fat, and perianal rash, consistent with failure to thrive. The anthropometry measurements at admission recorded weight as 2.30 kg, head circumference as 35 cm, and length as 44 cm, all significantly below normal parameters for age.

On chest auscultation, air entry was equal bilaterally with normal heart sounds. The abdomen was soft without organomegaly. Neurological examination showed appropriate cry, tone, activity, and newborn reflexes for gestational age. No obvious external congenital anomalies were detected1. During subsequent readmission for respiratory symptoms, examination revealed cold symptoms with bilateral crackles on chest auscultation, nasal blockage, and respiratory distress requiring intervention.

DIAGNOSTIC ASSESSMENT

A comprehensive diagnostic approach was undertaken to evaluate the failure to thrive and associated symptoms. Initial laboratory investigations included complete blood count, which showed hemoglobin of 12.4 g/dL, packed cell volume of 38.2%, total leukocyte count of 9,500 cells/mm³, and platelet count of 830,000/mm³. C-reactive protein was negative at 1.6 mg/L1. Liver function tests revealed mildly elevated liver enzymes with SGOT of 58 U/L, SGPT of 51 U/L, alkaline phosphatase of 137 U/L, total protein of 4.8 g/dL, and serum albumin of 2.9 g/dL, suggesting nutritional compromise.

The metabolic workup included stool examination for reducing substances and fat globules, both of which were negative, ruling out carbohydrate intolerance and fat malabsorption respectively. Arterial blood gas analysis showed no metabolic acidosis, and serum electrolytes were normal, effectively excluding renal tubular acidosis as a potential cause.

Urinalysis revealed 2-3 pus cells per high-power field, and urine culture grew Escherichia coli, confirming urosepsis. Ultrasound of the abdomen demonstrated internal echoes within the urinary bladder, consistent with cystitis. Blood culture showed no growth after 48 hours of incubation.

During subsequent evaluation for respiratory symptoms, chest radiographs revealed bilateral infiltrates and, notably, multiple radiopaque substances throughout the lung fields. This unexpected finding prompted further investigation with high-resolution computed tomography (HRCT) of the thorax, which identified "multiple small radiodense foci seen within lung parenchyma of medial basal segment of right lower lobe-likely foreign bodies," raising suspicion for mercury inhalation2. Serum mercury levels were measured and found to be significantly elevated at 33.6 μg/L (reference range: <10 μg/L), confirming mercury poisoning.

Neurosonography performed on day 74 of life showed a tiny choroid plexus cyst measuring 2.5 × 2 mm in the left lateral ventricle, which was considered an incidental finding1. Echocardiography performed on day 79 of life revealed normal cardiac structure and function1. Thyroid function tests and extended newborn screening were reported as normal.

Follow-up hemogram before discharge showed hemoglobin had decreased to 7.8 g/dL with a packed cell volume of 25.5%, necessitating blood transfusion.

INTERVENTIONS

The therapeutic approach was multifaceted, addressing the multiple clinical issues identified. For the failure to thrive, nutritional intervention included optimized feeding with a combination of breast milk and hydrolyzed formula (Aptamil Pepti) with human milk fortifier added to breast milk. The feeding technique was modified with palady (a specialized feeding cup) initially, followed by a gradual transition to direct breastfeeding.

For the lower respiratory tract infection and chemical pneumonitis secondary to mercury inhalation, respiratory support included oxygen therapy, initially via nasal prongs and subsequently requiring continuous positive airway pressure (CPAP) support for 12 hours following bronchoscopy. Nebulization therapy with levosalbutamol, 3% hypertonic saline, and budesonide was administered along with mucolytic medications and nasal decongestants.

The urosepsis was treated with intravenous antibiotics, initially amikacin and then piperacillin-tazobactam based on urine culture sensitivity showing Escherichia coli. The subsequent blood culture-positive sepsis with Staphylococcus haemolyticus was treated with the addition of intravenous linezolid.

For mercury poisoning, chelation therapy was initiated with British Anti-Lewisite (BAL or dimercaprol) at a dosage of 3 mg/kg/dose administered intramuscularly every 4 hours on day 1, followed by every 8 hours on day 2. The treatment plan included continuation with 0.4 ml of BAL (after diluting 1 ml [50 mg] with 2 ml of distilled water) every 12 hours for 10 additional days after discharge.

The anemia was corrected with transfusion of irradiated leukocyte-reduced packed red blood cells, administered at 14 ml/hour over 5 hours.

Supportive care included monitoring of vital signs, maintenance of thermoregulation with warmer care when needed, and additional nutritional supplements including vitamin D3, multivitamins, and calcium supplements.

FOLLOW-UP AND OUTCOMES:

The infant showed gradual improvement with the multifaceted therapeutic approach. During the initial hospitalization for failure to thrive, the baby demonstrated a weight gain of approximately 15 grams per day over 9 days, with the discharge weight recorded as 2.43 kg. Following the subsequent admission and treatment for mercury poisoning and associated complications, the weight increased further to 3.43 kg, though still below the 3rd percentile for age.

The respiratory symptoms improved with the implemented measures, with the infant maintaining oxygen saturation without supplemental oxygen at the time of discharge. The bronchoscopy procedure successfully identified and addressed the mercury deposits in the lungs, though follow-up imaging was planned to assess the resolution of the radiographic abnormalities.

The anemia improved following blood transfusion, with planned follow-up to monitor hematological parameters. The infection parameters normalized, with repeat C-reactive protein remaining negative at 1 mg/L. The baby was discharged with a comprehensive medication regimen including continuation of chelation therapy with BAL administered intramuscularly every 12 hours for 10 days, as well as supportive medications and supplements.

The parents were counseled regarding the importance of follow-up visits, monitoring for warning signs requiring immediate medical attention, and proper feeding techniques. A follow-up visit was scheduled with a pediatric specialist three days after discharge, with instructions to return sooner if any concerning symptoms developed.

This case presents several noteworthy aspects regarding the recognition and management of mercury poisoning in infants, which is relatively rare but carries significant morbidity. The initial presentation of failure to thrive without apparent cause necessitated a thorough investigation, illustrating the importance of comprehensive evaluation in cases of inadequate weight gain in infants. The subsequent discovery of mercury poisoning through radiological findings highlights the value of imaging studies in identifying unexpected environmental exposures.

Mercury toxicity in infants can manifest through various systems, with pulmonary involvement being particularly prominent in cases of inhalational exposure. The chemical pneumonitis observed in this case is consistent with the irritant effects of mercury vapor on respiratory epithelium, causing inflammation and increased secretions. The systemic absorption can subsequently lead to multiorgan involvement, including hematological effects as evidenced by the anemia in this patient.

The diagnostic approach in this case exemplifies the value of sequential investigation guided by clinical findings. The unexpected discovery of radiopaque substances on chest imaging prompted specific testing for heavy metal poisoning, leading to the confirmation of mercury toxicity with serum levels significantly above the reference range. This reinforces the importance of considering environmental toxin exposure in cases with unusual clinical or radiological presentations, particularly in infants who may not have the developmental capacity to avoid hazardous exposures.

The management approach demonstrates the integration of supportive care with specific interventions for mercury poisoning. Chelation therapy with BAL represents the standard of care for inorganic mercury poisoning, binding to mercury to form stable complexes that can be excreted. The administration schedule follows established protocols, with more frequent dosing initially followed by extended treatment at reduced frequency to ensure adequate elimination of the toxin.

The nutritional intervention for failure to thrive was equally important, with a structured approach to optimize caloric intake and absorption. The observed weight gain during hospitalization confirms the effectiveness of the nutritional plan, though continued monitoring is essential given the initial severity of growth faltering.

The case also highlights the importance of family education and follow-up care in managing complex pediatric conditions. The detailed discharge instructions and scheduled follow-up visits are crucial components of ongoing care, particularly for a condition requiring extended treatment such as chelation therapy.

This case report illustrates the complex presentation and management of mercury poisoning in an infant initially presenting with failure to thrive. The recognition of radiographic artifacts as potential indicators of heavy metal exposure was pivotal in diagnosis and subsequent therapeutic planning. The case emphasizes the importance of considering environmental toxins in the differential diagnosis of infants with failure to thrive and unusual radiological findings.

The successful management through a multidisciplinary approach including nutritional optimization, respiratory support, antimicrobial therapy, chelation, and hematological intervention demonstrates the importance of comprehensive care in addressing multisystem involvement. The case further highlights the need for thorough investigation in cases of failure to thrive without apparent cause, with imaging studies potentially revealing unexpected findings that guide diagnosis.

For clinicians, this case reinforces the value of maintaining a high index of suspicion for environmental exposures, particularly in pediatric populations where history may be limited and presentations atypical. The successful outcome underscores the importance of prompt recognition and appropriate intervention, with continued follow-up to monitor for long-term sequelae of mercury exposure, particularly neurodevelopmental outcomes which may manifest later in childhood.

Future research directions might include investigation of improved chelation protocols for infants, long-term neurodevelopmental outcomes following early mercury exposure, and enhanced screening methods for environmental toxins in cases of failure to thrive with respiratory symptoms.

The case of Baby Noushin thus serves as an important reminder of the potential impact of environmental exposures on infant health and the critical importance of thorough diagnostic evaluation and comprehensive management in achieving favorable outcomes.

The parents provided written informed consent for the publication of this case report, understanding that all identifying information would be appropriately anonymized while maintaining the scientific integrity of the report.

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