Patient: 7-year-old female Chief Complaint: Recurrent respiratory infections and chronic diarrhea. History of Present Illness: The patient has experienced multiple episodes of otitis media, sinusitis, and pneumonia since infancy. Over the past year, she has had three hospitalizations for pneumonia requiring intravenous antibiotics. Additionally, she has suffered from chronic diarrhea for the past six months, leading to weight loss and growth delays. There is no history of skin infections or abscesses. Past Medical History: • No known chronic illnesses. • Incomplete vaccination history due to frequent illnesses. Medications: • Occasional courses of antibiotics for infections. Family History: • Non-consanguineous parents. • No family history of immunodeficiency or recurrent infections. Social History: • Attends school; frequent absences due to illness. • No exposure to tobacco smoke or known environmental hazards. Physical Examination: • Vital Signs: Temperature: 37.8°C; Heart Rate: 110 bpm; Respiratory Rate: 22/min; Blood Pressure: 100/60 mmHg. • General: Pale, thin, and appears fatigued. • Growth Parameters: Below the 5th percentile for age in both height and weight. • HEENT: Mild cervical lymphadenopathy; tympanic membranes dull with mild erythema bilaterally. • Respiratory: Crackles heard in the right lower lung field. • Abdomen: Soft, non-tender; mild hepatomegaly noted. • Skin: No rashes or lesions. Laboratory Investigations: • Complete Blood Count (CBC): • Hemoglobin: 10.5 g/dL (low) • White Blood Cell Count: 6,000/µL • Platelets: 250,000/µL • Serum Immunoglobulins: • IgM: Elevated • IgG: Low • IgA: Low • Flow Cytometry: • Normal B and T cell numbers. • Genetic Testing: • Homozygous mutation identified on chromosome 20 • Stool Analysis: • Positive for Cryptosporidium antigen. What is the most likely diagnosis?
