Diagnosing asymmetrical neck swelling in a small child

A small boy aged 4 years was brought by his aunty for neck pain and swelling. It all started 4 days earlier with right periauricular pain. To this, added a swelling of that area and fever two days later. Temperature was 39 degrees Celsius, dropped temporarily after intake of Paracetamol. The following day, swelling extended to the posterior mandibular region and similar pains started in the left periauricular region leading to this consultation.
The child is a lone child to his mum, born vaginally. No documented history of pregnancy. Had exclusive breastfeeding for barely 2 weeks, then mixed milk feeding. Now takes family dishes. Never been hospitalized before. Stopped immunization after the free vaccines for infants. No notion of previous similar swelling in the boy. Deworming was done 3 months ago. Psychomotor development is okay for age.
There is no known chronic disease in mother. Father does not live with child and little is know about him.
There is a notion of bilateral swelling around the ears in another child in the same house about 3 weeks ago.
On clinical exam, child has anorexia, fatigue, no dysphagia, urine is clear yellow and there is no dysuria.
Stable vitals. Weight:15kg
The conjunctivae are coloured, Sclerae white. Tympanic membranes are not congested and tonsils are not inflammed. No caries are seen on teeth. Neck asymmetry with pronounced firm swelling on right periauricular and mandibular region, warm, tender and more prominent towards mandible. Mildly tender left periauricular region. Bilateral cervical lymphadenopathies. Chest is symmetric, lungs clear, heart sounds S1,S2 present and regular. The abdomen is non-distended, no mass palpable and bowel sounds of normal intensity. There is a scaly plaque on the mid portion of left leg. The testes are felt in scroti and there is no sign of localized inflammation.
The rest of exam was unremarkable.

STOP, THINK AND DIAGNOSE

Diagnosis was Mumps.
Differential was early manifestations of HIV infection. Next differential was a mandibular abcess, then infected lymph node. As last differential a Burkett of Burkett-like lymphoma can be considered.

A Full Blood Count and HIV serology were requested, and right neck ultrasound to evaluate swelling and surrounding.

The HIV test done on site was negative. The patient was placed on Paracetamol doses for weight every 6 hours for 3 days. Counseling was done for isolation from other children at home.
Close follow-up was to be programmed pending work-up results.

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