A 25-year-old woman develops fever, joint pain, and a rash 8 days after receiving antivenom for a snakebite. She has no prior history of allergic reactions. Laboratory tests show elevated ESR and C-reactive protein (CRP). Which of the following is the most likely underlying mechanism of her condition?

A 12-year-old boy presents with fever, rash, joint pain, and swelling 10 days after receiving a course of amoxicillin for a streptococcal throat infection. His mother reports that he has never taken penicillin before. On examination, he has generalized urticaria, mild arthralgia, and palpable lymph nodes. What is the most likely diagnosis?

A newborn is flagged during routine screening for low T-cell receptor excision circles (TRECs). The baby appears healthy but is referred for further evaluation. Flow cytometry confirms absent T-cells, normal B-cell counts, and absent NK cells. The parents are asymptomatic, and the baby has no other abnormalities. What is the most appropriate next step in management for this infant?

 A 2-month-old infant presents with recurrent pneumonia and oral thrush. The parents report poor weight gain and persistent diarrhea. Physical examination reveals a lack of tonsils and palpable lymph nodes. Laboratory results show low T-cell, B-cell, and NK-cell counts. The patient is diagnosed with adenosine deaminase (ADA) deficiency. Which of the following is a key pathological feature in this form of SCID?

A 3-month-old male infant is brought to the clinic with a history of recurrent respiratory infections, chronic diarrhea, and failure to thrive. Physical examination reveals absent tonsils and lymph nodes. Blood tests show lymphopenia, with low T-cell counts, normal B-cell counts, and low NK-cell counts. Genetic testing reveals a mutation in the IL2RG gene.What is the most likely diagnosis?

A 6-month-old infant is brought to the clinic due to frequent and severe infections since birth. Diagnostic tests reveal an absence of T-cells and B-cells, and the child’s blood work shows significantly elevated levels of deoxyadenosine. What genetic condition is most likely responsible for these findings?

A 6-month-old infant is brought to the clinic due to persistent diarrhea, recurrent respiratory infections, and failure to thrive. Laboratory evaluation shows very low levels of circulating B and T cells. Flow cytometry reveals decreased CD3+ and CD19+ cells. Genetic analysis confirms an adenosine deaminase deficiency. What is the most likely diagnosis?

A newborn female is evaluated for poor feeding, a weak cry, and hypotonia. Physical examination reveals a cleft palate, hypertelorism (wide-set eyes), a broad nasal bridge, and micrognathia (small jaw). A harsh systolic murmur is heard along the left upper sternal border. Laboratory testing shows severe hypocalcemia. An echocardiogram confirms truncus arteriosus. Which of the following statements is correct regarding the most likely etiology of this patient’s condition?

A 3-month-old infant is admitted with seizures. On examination, the child has micrognathia (small jaw), low-set ears, and a heart murmur. Lab results show hypocalcemia, and further tests reveal a low T-cell count. Genetic testing confirms a 22q11.2 deletion. What is the most appropriate initial management of this patient’s hypocalcemia?

An 8-year-old boy with a history of heart surgery for Tetralogy of Fallot shows signs of immunodeficiency with recurrent respiratory infections. Which of the following immunological findings would you expect in this patient with DiGeorge Syndrome?