What gastrointestinal issues could cause a 15-year-old boy to have chronic neutropenia (low neutrophil count) and monocytosis (high monocyte count)?

Gastrointestinal Causes of Chronic Neutropenia and Monocytosis in an Adolescent

In a 15-year-old boy living in Mexico with chronic neutropenia and monocytosis, the most critical GI-related considerations are chronic parasitic infections (particularly amebiasis and giardiasis), chronic bacterial infections including tuberculosis, and autoimmune neutropenia with secondary GI involvement.

Primary Infectious Considerations in a Traveler/Resident in Mexico

Parasitic Infections

• Chronic parasitic infections are a key consideration in patients from or residing in endemic areas like Mexico, as these can cause both neutropenia and monocytosis 1
• Amoebae and giardia are specifically identified as pathogens that can cause GI symptoms in immunosuppressed patients, though they can also be primary causes of chronic inflammation 1
• These infections may present with chronic diarrhea, abdominal pain, and systemic inflammatory responses that alter white blood cell distributions 1

Tuberculosis and Chronic Bacterial Infections

• Tuberculous involvement of the GI tract should be strongly considered, particularly given Mexico's higher TB prevalence compared to the United States 1
• TB can cause chronic inflammation leading to bone marrow suppression with neutropenia and compensatory monocytosis 1
• Children with TB often have a history of recent tuberculosis contact, and their family often originates from areas with high TB incidence 1

Malaria Consideration

• While less common in most of Mexico, malaria should be excluded if the patient traveled to endemic regions, as malaria pigment in neutrophils and monocytes can be a diagnostic clue 1
• Thrombocytopenia often accompanies malaria and may provide an additional diagnostic hint 1

Chronic GI Inflammatory Conditions

Inflammatory Bowel Disease

• Chronic inflammatory bowel disease can present with neutropenia and monocytosis, particularly in the context of chronic inflammation and malnutrition 2
• Monocytosis is specifically associated with GI disease, infections, and chronic inflammatory states 2

Autoimmune Neutropenia with GI Manifestations

• Autoimmune neutropenia of infancy/childhood is the most common cause of chronic neutropenia in this age group and frequently presents with monocytosis 3
• The median age at diagnosis is 8 months, but cases can present up to 30 months, and many patients have monocytosis as a compensatory mechanism 3
• These patients manifest recurrent fever and infections, with selective neutropenia (ANC 0-500) and many demonstrate monocytosis 3
• While typically diagnosed earlier, delayed recognition into adolescence is possible, particularly if infections have been mild 4

Critical Diagnostic Approach

Immediate Infectious Workup

• Stool studies are essential: examination for ova and parasites (multiple samples), bacterial culture, and consideration of specialized testing for amoebae and giardia 1
• TB screening: tuberculin skin test or interferon-gamma release assay, with consideration of GI TB if symptoms warrant 1
• Blood cultures if febrile, as approximately 50-60% of febrile neutropenic patients have occult infection 1, 5

Hematologic Evaluation

• Bone marrow examination may be necessary to evaluate for myeloid hyperplasia with maturation arrest (typical of autoimmune neutropenia) versus infiltrative processes 3
• Neutrophil antibody testing should be performed, as it establishes the diagnosis of autoimmune neutropenia in the majority of cases 3
• Serial complete blood counts to document chronicity and assess for other cytopenias 6

Imaging Considerations

• Abdominal imaging (ultrasound or CT) may identify hepatosplenomegaly, lymphadenopathy, or bowel wall thickening suggestive of chronic infection or inflammation 1
• Chest radiograph to evaluate for pulmonary TB 1

Important Clinical Pitfalls

Infection Risk Assessment

• The infection risk is inversely proportional to the neutrophil count, with greatest risk when ANC is below 100/µL 1, 5, 7
• Duration of neutropenia is critical—prolonged neutropenia (>10 days) significantly increases infection risk 7
• Common infection sites include the alimentary tract, sinuses, lungs, and skin 1, 5, 7

Specific GI Complications in Neutropenia

• Anorectal sepsis is a frequently forgotten cause of morbidity in neutropenic patients and requires clinical assessment by an experienced surgeon, potentially supplemented by MRI 1
• Neutropenic enterocolitis (typhlitis) can occur but is more common in chemotherapy-induced neutropenia rather than chronic idiopathic cases 1, 5
• C. difficile infection may have atypical presentation in neutropenic patients, as pseudomembrane formation requires neutrophil involvement 1

Drug-Related Causes

• Metronidazole, commonly used for parasitic infections, can cause reversible neutropenia and should be considered if the patient has been treated empirically 8
• Review all medications for potential myelosuppressive effects 4

Management Priorities

Empiric Treatment Considerations

• If chronic parasitic infection is suspected based on epidemiology and symptoms, empiric treatment may be warranted while awaiting definitive diagnosis, given the potential for serious complications 1
• For suspected TB with systemic symptoms, specialist consultation should be obtained regarding empiric treatment 1

Monitoring and Follow-up

• Serial neutrophil counts are essential to document trends and assess response to treatment 6
• If autoimmune neutropenia is diagnosed, spontaneous recovery typically occurs by age 4-5 years, with median duration of 20 months 3
• Patients require education about infection risk and when to seek immediate medical attention 1