cPAN can affect all ages with the average age of diagnosis being 40-50
years old with a greater predominance in women [2]. The estimated
prevalence is 31 cases in 1 million, and it is estimated that it
accounts for 4% of all cases of polyarteritis nodosa [3]. In
contrast to PAN, cPAN is limited to the skin and associated muscles and
joints surrounding the affected area [2]. Clinical signs include
tender subcutaneous nodules typically affecting the lower limbs, which
may progress to ulceration in 50% of the cases [1]. Other
dermatological features include livedo reticularis, livedo racemosa and
purpura [1]. Late- stage features are necrosis, neuropathy, myositis
and neuritis [1]. cPAN can be distinguished from sPAN by its lack of
systemic involvement, hypertension, bullae, livedo reticularis gangrene
of extremities, leucocytosis and eosinophilia [2]. Unlike PAN, it is
not fatal if left untreated but follows a benign course that may either
become chronic or relapsing and remitting over several years [1].
Multiple associations with cPAN include group A beta haemolytic
streptococcus infections, hepatitis B and C, inflammatory bowel disease,
CMV, parvovirus B19, tuberculosis, malaria, and drugs such as
minocycline, sulphonamides and IV amphetamines [1, 2]. An incisional
biopsy to deep fat for histopathology is mandatory to establish the
diagnosis, as well as tissue biopsy for microbial culture depending on
the clinical context. Differential diagnoses for other forms of small to
medium vessel vasculitis include lymphocytic thrombophilic arteritis,
panniculitis, venous thrombosis and atypical infection. Further
investigations should include; cryoglobulins, ANA, ANCA, RF and
complement levels to exclude secondary causes [1-2, 4]; and; imaging
to exclude systemic organ involvement.
There is no consensus on initial treatment, dosage, length of treatment,
or specific drug combination [5, 6]. Current studies have noted that
mild cPAN can be adequately treated with NSAIDs, colchicine, topical
corticosteroids, and low dose corticosteroids [1, 4, 6]. The
presence of ulceration in the initial episode predicts an increased risk
of relapse and is associated with a worse prognosis [7]. In such
patients, case series have demonstrated up to 1mg/kg/day of prednisone
was associated with a significant reduction of pain, disappearance of
subcutaneous
nodules and significant improvement of cutaneous ulcers [1, 8]. For
patients who were refractory to prednisone, the addition of IV
cyclophosphamide, azathioprine and IVIG have been shown to induce
remission [5-6, 9]. Studies have also advised for aggressive
treatment for patients who had constitutional symptoms, severe course of
disease or high acute phase reactants [5, 6]. Studies have found
that a flare of cPAN usually follows attempts to wean prednisone
[8]. Steroid sparing agents include colchicine, hydroxychloroquine,
methotrexate, sulphapyridine, pentoxifylline and dapsone [1, 4-5].
Patients with cPAN should be followed up twice yearly and have regular
surveillance to exclude possible progress to systemic PAN [1]. The
likelihood of cPAN progressing to sPAN is rare. In a large case series
examining 79 patients with cPAN there was no progression to systemic PAN
in a follow-up period of up to 30 years [8]. However, a case series
noted that patients have developed sPAN up to 19 years after the initial
diagnosis [10].