A 20-Year-Old Man With a Dark, Burning Rash

Christian Beebe, MD, MBA

Disclosures

August 13, 2015

Discussion

Several guidelines are available for the diagnosis of Henoch-Schönlein purpura.[1] The American College of Rheumatology (ACR) requires four criteria (published in 1990) for diagnosing Henoch-Schönlein purpura[2]: palpable purpura, patient age of 20 years or younger at onset, bowel angina, and the presence of granulocytes in the vessel walls.

In 2006, the European League Against Rheumatism (EULAR) and the Pediatric Rheumatology Society published their own criteria for diagnosis of Henoch-Schönlein purpura. These include palpable purpura as a mandatory criterion, with at least one of the following conditions: diffuse abdominal pain, predominant IgA deposition (confirmed on biopsy), acute arthritis in any joint, and renal involvement (as evidenced by hematuria and/or proteinuria).[3]

According to the older ACR criteria, the diagnosis of Henoch-Schönlein purpura for this patient could be called into question, because he exhibited no bowel symptoms. However, according to the more recent EULAR criteria, this patient fits the diagnosis of Henoch-Schönlein purpura quite well, because he has palpable purpura, predominant IgA deposition confirmed on biopsy, monoarticular arthralgia in his right ankle, and renal involvement.

The sine qua non for the diagnosis of Henoch-Schönlein purpura is the staining of vessels with IgA in the context of a leukocytoclastic vasculitis. A skin biopsy with immunofluorescence studies is recommended if Henoch-Schönlein purpura is clinically suspected.[4] The etiology of the disease remains unknown, but it is understood to be an autoimmune response (usually to an upper respiratory infection).

Other items in the differential diagnosis include many of the etiologies of palpable purpura. An algorithmic attempt has been made to delineate these etiologies, but classification remains difficult,[5] because many entities can cause it (Table 1).[6]

Table 1. Etiology of Purpura

Intravascular (usually nonpalpable) ▪ Alterations in platelet formation, destruction, or function
▪ Drugs (aspirin, methyldopa)
Idiopathic thrombocytopenic purpura
Thrombotic thrombocytopenic purpura
Disseminated intravascular coagulation
▪ Infection (especially Neisseria, Rickettsia, Staphylococcus)
▪ Splenic sequestration
▪ Radiation therapy
▪ Myelofibrosis
Myeloproliferative disorders
Vascular (usually palpable) Inflammatory vascular causes
▪ Cutaneous vasculitis ▪ Purely cutaneous vasculitis (eg, secondary to medications)
▪ Henoch-Schönlein purpura
Polyarteritis nodosa
▪ Granulomatous vasculitis (Wegener granulomatosis, Churg-Strauss vasculitis)
▪ Cutaneous vasculitis associated with a collagen
▪ Vascular disease (eg, systemic lupus erythematosus, rheumatoid arthritis)
▪ Giant cell arteritis
▪ Mixed cryoglobulinemia
▪ Hyperglobulinemic purpura
Noninflammatory vascular causes
▪ Trauma
▪ Subacute bacterial endocarditis
▪ Other embolic diseases
▪ Amyloidosis
Extravascular and miscellaneous (may be palpable or nonpalpable) ▪ Corticosteroids
▪ Toxins and venoms
▪ Senile purpura
▪ Scurvy
▪ Valsalva maneuver
▪ Pseudopurpura (Sweet syndrome, cherry angiomas, angiokeratoma, Kaposi sarcoma)

Derived from Schreiner DT. Dermatol Clin. 1989;7:481-490.[6]

Additional information can be gleaned from the pathologic diagnosis of small-vessel vasculitis, which carries its own differential diagnosis (Table 2).[7]

Table 2. Clinical Signs of Necrotizing Vasculitis With Respect to Vessel Size Involved

Small Vessels
Signs Diseases
Urticaria Hypersensitivity vasculitis
Palpable purpura ▪ Henoch-Schönlein purpura
▪ Essential mixed cryoglobulinemia
▪ Vasculitis associated with connective tissue disease
▪ Vasculitis associated with cancer
▪ Serum sickness and serum sickness-like reactions
Nodules, bullae, or ulcers Chronic urticaria (urticarial vasculitis)
▪ Urticarial prodrome of acute hepatitis type B infection
Large Vessels
Signs Diseases
Subcutaneous nodules, ulceration, and ecchymoses ▪ Polyarteritis nodosa
▪ Churg-Strauss syndrome
▪ Wegener granulomatosis
Giant cell (temporal) arteritis

Derived from Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. St Louis: Mosby; 2004.[7]

The intersection of these two differential diagnoses consists of mixed cryoglobulinemia, vasculitis associated with collagen vascular disease (ie, systemic lupus erythematosus, rheumatoid arthritis), and Henoch-Schönlein purpura.

Mixed cryoglobulinemia was easily ruled out, because the patient's serum cryoglobulin test and complement levels revealed a normal C3 of 118 mg/dL (normal range, 79-152 mg/dL), a C4 of 26 mg/dL (normal range, 16-38 mg/dL), and total hemolytic complement CH50 of 53.0 U/mL (normal range, 22-60 U/mL), as well as a negative serum cryoglobulin result.

Another diagnosis that was readily excluded was systemic lupus erythematosus. This patient had only one arthralgia, and no fever, myalgia, or malaise was noted; only one of the 11 ACR criteria for the diagnosis of lupus was met.[8] To satisfy the clinical diagnosis of systemic lupus erythematosus, four of the 11 ACR criteria are required.[8]

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