Perls' ferrocyanide test for iron in the diagnosis of vasculitic neuropathy.

Preliminary observations suggested that arterial and arteriolar necrosis in vasculitis of the peripheral nerve leads to local haemorrhage and subsequent deposition of haemosiderin. This pigment is more readily recognized in the nerve by the sensitive Perls' test for iron than by relying on recognizing its yellow colour. To support the use of iron staining as an index of vasculitis, in addition to necrosis and fibrin deposition, we obtained the following results from nerve biopsy and autopsy nerve specimens: vasculitis confined to PNS = 5/6 iron positive; polyarteritis nodosa and Wegener's granulomatosis = 4/5 iron positive; systemic lupus erythematosus 2/3 iron positive; rheumatoid disease 1/1 iron positive; acute Guillain-Barré syndrome and subacute or chronic demyelinating polyradiculoneuropathy = 12/12 iron negative; and other perivascular inflammation in the PNS (without evidence of vasculitis) = 2/2 iron negative. One case of Churg-Strauss syndrome showed no changes on nerve biopsy. Iron staining was also demonstrated in the kidneys of five or six patients with polyarteritis nodosa.