Intended for healthcare professionals

Endgames Spot Diagnosis

A boy with purpura on the legs

BMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n329 (Published 04 March 2021) Cite this as: BMJ 2021;372:n329
  1. Yan Song, nephrologist1,
  2. Qin Zhou, renal pathologist1,
  3. Jianjun Qiao, dermatologist2,
  4. Jianghua Chen, professor1
  1. 1Kidney Disease Center, The First Affiliated Hospital, Zhejiang University, Hangzhou, China
  2. 2Department of Dermatology, The First Affiliated Hospital, Zhejiang University, Hangzhou, China
  1. Correspondence to: J Chen azjukidney{at}zju.edu.cn

A boy in his mid teens presented to the dermatology department with a one week history of non-pruritic rash on his legs, and abdominal and bilateral knee pain. On examination, palpable purple papules were present on both legs, extending from the ankles to the thighs (fig 1). Other examination findings were unremarkable. The boy reported no history of upper respiratory tract infection in the four weeks before symptom onset. Table 1 shows the results of relevant blood and urine investigations.

Fig 1
Fig 1

Palpable purpura on lower legs

Table 1

Results of relevant blood and urine investigations

View this table:

Several conditions were considered unlikely: meningococcal sepsis, because of the absence of fever, neurological symptoms, and biomarkers of bacterial infection; thrombocytopenia, because the platelet count was within normal range; and coagulopathy, because coagulation biomarker levels were within normal range.

Because the rash distribution was considered extensive and therefore atypical, a cutaneous biopsy specimen was taken of a papule to differentiate between vasculitis, vasculopathy, and embolism.1 The sample showed leucocytoclastic vasculitis.

As the patient’s proteinuria level was high (2.36 g) a renal biopsy sample was taken.1 This showed crescents and infiltration of lymphocytes and neutrophils around the capillaries and glomeruli (fig 2). Immunofluorescent staining of the specimens showed IgA deposition in postcapillary venules.

Fig 2
Fig 2

Histopathological examination of a renal biopsy specimen, showing crescents (black circles) and infiltration of lymphocytes and neutrophils around capillaries and glomeruli (black arrows)

Question

What is the most likely diagnosis?

Answer

Immunoglobulin A vasculitis.

Immunoglobulin A vasculitis, previously known as Henoch-Schönlein purpura, mainly involves the skin, kidneys, gastrointestinal tract, and joints.2 The annual incidence is 326.7 per 100 000 in children and 0.8-1.8 per 100 000 in those aged 16 years or older.2

Immunoglobulin A vasculitis is generally self-limiting and resolves within an average of four weeks. It is characterised by immunoglobulin A deposition in postcapillary venules, accompanied by leucocytoclasis. Immunoglobulin A vasculitis is a systemic small vasculitis that features palpable purpura, renal damage, joint pain (80%),23 and abdominal pain (70%).3 Upper respiratory tract infections often precede symptom onset by one to two weeks.3

Palpable purpura, which quickly develops from pink to red papules, is symmetrically distributed, often appears in crops, and occurs mainly on the legs and buttocks and occasionally on the arms and trunk.24 The papules typically subside within two weeks but might evolve to bullae and necrotic rash.45

Levels of serum immunoglobulin A might be increased in at least half of patients.13 A positive faecal occult blood test result indicates gastrointestinal tract involvement.13

As a priority rule out meningococcal sepsis, profound thrombocytopenia, and coagulopathy as other causes of an acute onset purpuric rash.145

Purpura with renal damage also occurs in cryoglobulinaemic vasculitis,46 systemic lupus erythematosus,7 Waldenström macroglobulinaemia,7 Wegener’s granulomatosis,78 Churg-Strauss syndrome,78 microscopic polyangiitis,78 and polyarteritis nodosa.789

Perform a renal biopsy if patients have severe proteinuria (>250 mg/mmol), persistent moderate proteinuria (100-250 mg/mmol) or impaired glomerular filtration rate.1

Consider skin biopsy in cases of atypical rash to exclude alternative diagnoses.1

Learning point

  • Consider immunoglobulin A vasculitis when patients present with multiple organ symptoms—namely, skin, kidney, joints, and gastrointestinal system.

Patient outcome

The patient received treatment with prednisone 40 mg daily. The cutaneous purpura, abdominal pain, and arthralgias improved substantially after a week. A stool test showed no red blood cells after a week. Blood cells and proteinuria were not detected by urinalysis tests after four weeks. The corticosteroid dose was tapered gradually and withdrawn after four months. The patient was followed up by nephrology with monthly urinalysis until a negative result for urine protein.

Footnotes

  • Competing interests: None declared.

  • Patient consent obtained.

References

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