Dermatology
Question 17 of 24
A 3 year old is brought into ED with a widespread rash. He recently had a fever and cold which resolved about 2 weeks ago. The rash initially started on his face and spread to his trunk and arms. On examination he is otherwise well and observations are normal. What is the most likely diagnosis?
Answer:
- Erythema infectiosum: Prodromal symptoms usually start around a week following exposure to parvovirus B19. They are usually mild and may include headache, rhinitis, sore throat, low-grade fever and malaise. Following the prodromal phase, patients are usually symptom-free for around 7-10 days and then the classic 'slapped cheek' rash usually appears as erythema on the cheeks, sparing the nose, perioral and periorbital regions. This disappears after 2-4 days. About 1-4 days after the facial rash appears, an erythematous macular/morbilliform rash develops on the extremities, mainly on the extensor surfaces.
Childhood Exanthems
Dermatology
Last Updated: 5th May 2022
Summary of Clinical Features
| Name | Infectious agent | Clinical features |
|---|---|---|
| Measles | Measles virus |
|
| Scarlet fever | Streptococcus pyogenes |
|
| Rubella | Rubella virus |
|
| Erythema infectiosum (fifth disease) | Parvovirus B19 |
|
| Roseola infantum (sixth disease) | Human herpesvirus (HHV)-6 and HHV-7 |
|
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
