A 19 year-old man presents with a 2 day history of "his fingers turning black" and
a 3-4 month history of recurrent painful lumps on his lower legs and a persistent
net-like rash over the calves and ankles which does not fade with pressure (see pictures,
below). His only other symptoms are fatigue and intermittent low grade fevers. He
denies abdominal pain, hematuria, dyspnea, chest pain or focal neurological deficits.
Six weeks before symptom onset, he had a self-limited sore throat.
DIAGNOSIS: Cutaneous polyarteritis nodosa (PAN) with livedo reticularis triggered
by a Group A streptococcal pharyngitis. PAN is a vasculitis involving deep medium
sized arteries. The diagnosis is best confirmed by doing a deep skin biopsy, since
the associated increase in inflammatory markers is non-specific. The diagnosis of
livedo reticularis can be confirmed at the bedside (physiologic livedo resolves with
warming; persistence with warming suggests pathology).
Necrosis of digits (left image) and subcutaenous nodules and livedo reticularis (right image)