What is the most likely diagnosis for a 2-year-old boy with recurrent episodes of fever, mouth sores, and scattered aphthous ulcers, occurring every 3 weeks and lasting 3 to 5 days, with a temperature of 38.4°C (101.2°F), tachycardia, and normal growth and development?

Differential Diagnosis

• Single most likely diagnosis + B) Cyclic neutropenia: This condition is characterized by recurrent episodes of neutropenia, which occur at regular intervals (usually every 21 days). The patient's symptoms, such as fever, mouth sores, and a history of similar episodes every 3 weeks, are consistent with cyclic neutropenia. The mostly cloudy laboratory result may indicate an infection, which is common in neutropenic patients.
• Other Likely diagnoses + H) Viral illness: The patient's symptoms, such as fever and mouth sores, could be caused by a viral illness. However, the recurrent nature of the episodes and the regular interval between them make cyclic neutropenia a more likely diagnosis. + F) Leukemia: Although leukemia can cause recurrent infections and mouth sores, the patient's growth and development are appropriate for age, and there is no lymphadenopathy, making this diagnosis less likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.) + G) Severe congenital neutropenia: This condition is characterized by a severe deficiency of neutrophils, which can lead to life-threatening infections. Although the patient's symptoms are not as severe as those typically seen in severe congenital neutropenia, it is essential to consider this diagnosis to ensure prompt treatment. + A) Chédiak-Higashi syndrome: This rare genetic disorder affects the immune system and can cause recurrent infections. Although it is unlikely, it is crucial to consider this diagnosis due to its potential severity.
• Rare diagnoses + C) Dyskeratosis congenita: This rare genetic disorder is characterized by skin hyperpigmentation, nail dystrophy, and oral leukoplakia. Although the patient has mouth sores, the absence of other characteristic features makes this diagnosis unlikely. + D) Fanconi syndrome: This rare genetic disorder affects the bone marrow and can cause neutropenia, but it is typically associated with other physical abnormalities and congenital anomalies, which are not present in this patient. + E) Hypersplenism: This condition is characterized by an overactive spleen, which can cause neutropenia. However, it is typically associated with splenomegaly, which is not mentioned in the patient's examination. + 1) Vitamin B12 (cobalamin) deficiency: This deficiency can cause neutropenia, but it is typically associated with other symptoms, such as fatigue, weakness, and neurological abnormalities, which are not present in this patient.