Skin & Subcutaneous Tissue

Frame 1

Lunchtime over, you head back to the pediatric clinic.  

"Shall I send the next patient in?", your nurse asks.

You respond in the affirmative and are introduced to six-year-old Simon, who is accompanied by his mother, Fiona.

Frame 2

Fiona says that Simon has had several "eruptions" on his face for the last three days.

He was completely well earlier, with unremarkable medical and surgical histories. All immunizations are up to date, and his growth and development are age-appropriate.

Frame 3

Simon's vital signs are as follows: pulse 100 bpm, respiratory rate 24 cpm, blood pressure 100/60 mmHg, oral temperature 97.7°F (36.5°C).

During the general examination, you notice two vesiculopustular lesions with an erythematous base on the right labial commissure. Both are around 1.5 cm in size. You also notice a honey-colored crust with a moist erythematous base over the right nostril. This is 2.0 cm in size.

Several small lymph nodes are palpable in the right submandibular region. They are mobile and non-tender.

Frame 4

The remainder of the physical examination is unremarkable.

You sit back and ponder what to do next.

Frame 5

What will you do now?

Choice Outcome Score Continues
Obtain a skin swab from underneath the crust Incorrect 0 → Frame 6
Obtain swabs of the nares and throat Incorrect 0 → Frame 6
Order no investigations for now Correct 1 → Frame 7

Frame 6

You decide to obtain a swab but then stop. After all, these are unable to differentiate between bacterial infection and colonization.

Frame 7

You realize that you can start treatment based on the clinical findings, and ponder what to prescribe.

Frame 8

What will you do now?

Choice Outcome Score Continues
Prescribe oral penicillin V Incorrect 0 → Frame 9
Prescribe oral clindamycin Incorrect 0 → Frame 9
Prescribe mupirocin ointment Correct 1 → Frame 10

Frame 9

You start to write our a prescription for oral antibiotics, but then stop.

Given the lack of systemic signs, a topical antibiotic is probably a better choice right now.

Frame 10

You inform Fiona that Simon most likely has impetigo and educate her about the disease.

You also prescribe topical mupirocin, advocate regular removal of the crusts with the frequent application of wet dressings, and stress on the importance of good hygiene.

Frame 11

Last but not least, you stress on the avoidance of close contacts, given the contagiousness of the disease.

Fiona thanks you and takes her leave, Simon in tow.

Frame 12

A week later, Simon is back for a review. Fiona has followed your advice to the letter, and the lesions have cleared almost completely.

Simon beams when you tell him that he can go back to school now.

Frame 13

Three weeks later, you are surprised to see Simon and Fiona back in front of you.

Fiona looks distraught. "Doctor, my son's face was swollen when he woke up today! He looked perfectly fine last night. Please tell me it's nothing serious?", she says.

"Don't worry Fiona. You did well in bringing Simon here. I'll take a quick look at him now and let you know, OK?", you speak soothingly. Fiona nods and visibly calms down.

Frame 14

After recovering from the impetigo, Simon was healthy until today. He feels nauseous and weak. Careful history taking additionally reveals that his urine was rather dark this morning.

His vital signs are as follows: pulse 140 bpm, respiratory rate 20 cpm, blood pressure 120/80, and oral temperature 97.7°F (36.5°C). His oxygen saturation is 99%, on ambient air. He is fully oriented in time, place, and person.

Frame 15

The general examination confirms mild symmetrical periorbital edema, as well as 2+ bilateral pitting ankle edema. During palpation the abdomen, Simon complains of mild discomfort of both flanks.

The remainder of the examination is normal.

Frame 16

What are you thinking of?

Choice Outcome Score Continues
Ig A nephropathy Incorrect 0 → Frame 17
Post-streptococcal glomerulonephritis Correct 1 → Frame 18
Tubulointerstitial nephritis Incorrect 0 → Frame 17

Frame 17

You turn towards Fiona and start to explain what you think the probable diagnosis is - but then close your mouth.

There is a more probable diagnosis!

Frame 18

You inform Fiona that Simon quite possibly has acute post-streptococcal glomerulonephritis (APSGN), and explain about the disease.

You state the need for hospital admission and further investigation, to which she provides consent.

Subsequently, you instruct your staff to make the relevant arrangements and in parallel, order a panel of laboratory studies. A short while later, Simon is sent over to your ward.

Frame 19

Not too long afterwards, the results of the laboratory tests are in your hards:

Complete blood count


WBC: 10,000/mm3 (4,300-10,800)

Hb: 14.1 g/dL (14.0-17.5)

Hct: 32% (33-44)

MCV: 85 fL (76-96)

MCH: 31 pg (27-32)

Plt: 225,000/mL (150-450)

Renal functions and electrolytes


BUN: 30 mg/dL (3-20)

Creatinine: 1.4 mg/dL (0.6-1.2)

Sodium: 148 mmol/L (135-145)

Potassium: 5.3 mmol/L (3.5-5)

Chloride: 100 mmol/L (95-105)

Calcium: 2 mmol/L (2-2.6)

Phosphate: 1.7 mmol/L (0.8-1.5)

Albumin: 3.3 g/dL (3.5-5.5)

C3: 60 mg/dL (88-252)

C4: 49 mg/dL (12-72)

ASOT: 359 IU/mL (normal ≤ 640)

Anti-DNase B: 503 IU/mL (normal ≤ 375)

Arterial blood gas assay


PO2: 90 mmHg (80-100)

PCO2: 45 mmHg (35-45)

HCO3: 23 mmHg (22-26)

pH: 7.37 (7.35-7.45)



Color: deep amber

Turbidity: cloudy

pH: 6.0 (5.5-6.5)

Specific gravity: 1030 (1010-1025)

Glucose, ketones: none

Nitrites, leukocyte esterase: negative

Bilirubin: negative

Urobilirubin: Minimal

Protein: ++

Urinalysis (contd)


RBCs: 30 RBCs/hpf (0-4)

WBCs: 3 WBCs/hpf (0-5)

Squamous epithelial cells: 14/hpf (0-20)

Casts: red cell and granular casts present

Crystals, bacteria, yeast: None

Frame 20

You note the presence of microscopic hematuria, elevated Anti-DNase B levels, and reduced C3 complement levels. This confirms the presence of APSGN.

Frame 21

You inform the nursing staff of the need for strict bedrest, careful fluid restriction, and a low-sodium, low-protein diet. You also write out an order for oral furosemide 2 mg/kg/day.

Frame 22

What else do you prescribe?

Choice Outcome Score Continues
Two doses of 5% albumin Incorrect 0 → Frame 24
Four weeks of prednisolone, with tapering Incorrect 0 → Frame 23
Ten days of oral penicillin V Correct 1 → Frame 25

Frame 23

You start to write out an order for oral prednisolone but then stop.

After all, it might be wise to observe the disease progression first.

Frame 24

You start to write out an order for albumin transfusions, but then stop.

Right now, Simon doesn't really need this.

Frame 25

You write out an order for oral penicillin V, aiming to eradicate any remaining strains of nephritogenic streptococci.

Frame 26

What else will you do?

Choice Outcome Score Continues
Obtain swabs from all close contacts Correct 1 → Frame 28
Start antibiotic therapy in all close contacts Incorrect 0 → Frame 27

Frame 27

You consider commencing antibiotic therapy in all close contacts but then stop.

Right now, you have a single case of APSGN - not an epidemic.

Frame 28

You decide to screen all close contacts for nephritogenic streptococci and make the necessary arrangements.

Frame 29

After four days of treatment Simon's condition has markedly improved. The periorbital edema and ankle edema have gone down significantly. His blood pressure is now 100/70 mmHg.

The latest urinalysis reveals persistent microhematuria (25 RBCs/hpf) and red cell and granular casts. All other investigations are normal.

Frame 30

You inform Fiona that her son has responded well to the therapy and that he can be discharged on low-dose diuretic therapy.

You also state that she will need to maintain a daily urine dipstick diary on his behalf, and schedule a follow-up appointment in a month's time.

Frame 31

During the follow-up appointment, you note that Simon's edema has subsided completely, while his vital signs are also normal.

His urine dipstick diary shows persistent microhematuria and mild proteinuria. A urinalysis performed on the preceding day is significant for 1+ protein, 15 RBCs/hpf, and red cell casts. His renal functions are normal, as are complement levels.

Frame 32

You inform Fiona that Simon's results are not unexpected and that this is a normal part of the recovery process.

You stop all treatment but emphasize that she should continue to maintain the urine dipstick diary and that you'll need to evaluate him on a monthly basis for a year, to make sure that chronic kidney disease does not set in.

Frame 33

Unfortunately, at the next appointment, you find out that the periorbital and ankle edema have slowly returned over time, although Simon remains asymptomatic. His blood pressure is 115/75 mmHg now.

The urine dipstick diary shows persistent microhematuria and proteinuria. A urinalysis performed one day ago shows 2+ protein, 18 RBCs/hpf, and red cell casts. Renal functions and complement levels are within normal parameters.

Frame 34

What will you do now?

Choice Outcome Score Continues
Order a DMSA scan Incorrect 0 → Frame 35
Order a DTPA scan Incorrect 0 → Frame 36
Order a renal biopsy Correct 1 → Frame 37

Frame 35

You consider ordering a DMSA scan to evaluate the gross structure and function of the kidneys but then stop.

You've realized that this investigation won't help you right now.

Frame 36

You consider ordering a DTPA scan to assess renal function but then stop.

This investigation isn't indicated right now!

Frame 37

You realize that a renal biopsy is indicated now and explain this to Fiona. She looks uncertain but provides consent after listening to you carefully and asking several questions.

You proceed to make the necessary arrangements.

A few days later, Simon and Fiona are in front of you once more, as are the results of the renal biopsy.

In around 50% of glomeruli, focal proliferation of glomerular epithelial cells form crescentic cellular masses that fill Bowman's space. Immunofluorescence reveals diffuse and irregular mesangial IgG and C3 deposits.

This histopathologic appearance is suggestive of immune complex-mediated rapidly progressive glomerulonephritis (RPGN), i.e. type 2 RPGN.

Frame 38

You put down the report and explain the implications to Fiona, who looks ready to burst into tears. You then gently explain that Simon will need to be admitted again, to which she consents.

Following admission, you start him on IV methylprednisolone, oral cyclophosphamide, and titrated loop diuretics. You also initiate plasma exchange therapy.

Frame 39

On the fifth day of admission, Simon's edema has subsided completely, while his blood pressure is 100/70 mmHg. A urinalysis shows 1+ proteinuria and 9 RBCs/hpf, with no cell casts. His 24-hour urine protein excretion is 150mg/day.

Frame 40

Because of this excellent response to therapy, you decide to discharge him. You inform Fiona that he will need two more weeks of plasma exchange, as well as monthly pulse regimens of cyclophosphamide for three months. He will also need to take oral prednisone for nine months.

Fiona asks you what the likely long-term outcome is.

Frame 41

How do you respond?

Choice Outcome Score Continues
Simon is quite likely to recover over time Correct 1 → Frame 43
Simon might recover - but it is more likely that he will need renal transplantation down the line Incorrect 0 → Frame 42
Simon is quite likely to need renal transplantation down the line Incorrect 0 → Frame 42

Frame 42

You start to inform Fiona that Simon has a high probability of requiring renal transplantation down the line, but then stop.

After all, his response to therapy suggests the exact opposite!

Frame 43

You tell Fiona that as Simon appears to have steroid-responsive glomerular disease, there is a high likelihood of a good outcome. Of course, this is contingent in his adhering to the treatment and follow-up.

Frame 44

A year later, Simon and his mother are back in front of you.

Simon's response to treatment has been excellent, and you've managed to wean him off steroids. His renal functions are still normal, and now, the urinalysis shows no traces of proteinuria or hematuria.

All in all, he is a medical success story.

Frame 45

As you tell Fiona the good news, she cannot stop thanking you.

Being a doctor might not be the easiest job in the world - but it is moments like this that make it all worth it.

Well done!

The end