The Purple Digit: An Algorithmic Approach to Diagnosis

Patrick J. Brown; Matthew J. Zirwas; Joseph C. English III

Disclosures

Am J Clin Dermatol. 2010;11(2):103-116. 

In This Article

3. Cold-mediated Injury

3.1 Frostbite

Frostbite occurs when tissues freeze after exposure to extreme cold. It is during the second stage of frostbite (thaw/rewarm) that digits are most likely to appear violaceous. From prior studies, we are able to predict that tissue loss will begin after 1 hour at a temperature of 201F (-7°C), but when cooling occurs by conduction (i.e. direct skin contact with sub-freezing material), this time can be shortened immensely.[50] Frostbite should be considered in the homeless (especially when improperly clothed), smokers, those with peripheral vascular disease, drug abusers, and intoxicated persons.[51] In one study, 69% of patients reporting to a Canadian emergency room with frostbite were under the influence of alcohol or had a psychiatric illness.[52] Mainstays of treatment include actively rewarming in a 1041F (401C) bath to limit tissue necrosis and prevention of secondary infection, with marginal benefit from vasodilators and anti-inflammatory medications.[53] Alteplase (tissue plasminogen activator) has been shown to improve tissue perfusion and reduce amputations when administered within 24 hours of injury, although this practice is not widespread.[54]

3.2 Non-freezing Injury

Chilblains (or pernio) occur after prolonged exposure of nonadapted tissue to above-freezing temperatures. Clinically, it presents as symmetric, tender, violaceous papules that coalesce to form plaques, most commonly on the dorsal aspect of the fingers and toes.[55] Pernio is usually a clinical diagnosis, but skin biopsy may be necessary to differentiate pernio from acral lesions of lupus erythematosus. Histologic hallmarks of pernio include a papillary and deep T-cell infiltrate with perieccrine reinforcement, dermal edema, and necrotic keratinocytes.[56] The only prospectively studied medication with proven efficacy is nifedipine, which has been shown to reduce perivascular lymphocytic infiltrates and prohibit formation of new lesions while promoting clearance of existing pernio.[57] The natural history of untreated pernio is resolution in 1–3 weeks in healthy adults.[58] In any refractory case of pernio, the non-disease-specific infiltrates of chronic myelogenous leukemia (CML)[59,60] and the specific skin eruption of a CML blast crisis[61] must be in the differential diagnosis. Also in the differential diagnosis of refractory pernio are sarcoidosis and cutaneous lupus.[61]

As discussed in section 2.1, acral lesions of systemic and cutaneous lupus erythematosus may affect the digits in various ways.[3] The type of lupus erythematosus most akin to the violaceous lesions of perniosis, for which it is often mistaken, is chilblain (Hutchinson) lupus.[62] Like pernio, chilblain lupus is initiated in cold, damp environments, but chilblain lupus is less likely to regress during warmer months.[63] Histologically, chilblain lupus can be differentiated from pernio by the presence of vacuolated basal cells, as well as a relative absence of the features common to pernio that are listed above.[56] Traditionally, chilblain lupus has been difficult to treat,[64] but case reports and anecdotal evidence suggest that mycophenolate mofetil[65] and thalidomide[3] may be more efficacious than antimalarials and corticosteroids.

Secondary vasospasm in patients with cryogelling disorders may lead to acrocyanosis[29,30] (figure 3), as mentioned in section 2.1, or Raynaud phenomenon.[66]These patients may also present with acute purple digits secondary to vaso-occlusive events. Cryoglobulins are immunoglobulins associated with plasma cell dyscrasias and lymphoproliferative disorders.Type I cryoglobulinemia is more likely to form non-inflammatory dermal vascular occlusion (retiform purpura) with hyaline-like intravascular deposits and to present as acute purple digits, while types II and III are more likely to cause inflammatory vascular lesions with palpable purpura[67] and to be associated with viral infections such as hepatitis C virus.[68] When occlusion occurs in the digital distribution, cryoglobulinemia can present as an acute purple digit.[69] Cryofibrinogenemia is a relatively common entity, especially in the hospitalized population, but overall is a relatively infrequent cause of cold-related occlusion syndromes.[70] Cryofibrinogenemia is associated with malignancy, infection, and systemic inflammatory processes,[71] and can progress to digital necrosis.[72] Patients with cold agglutinins often have a history of Mycoplasma infection or mononucleosis.[73,74] There is an increased suspicion for underlying malignancy when patients are >60 years old with chronic cold agglutination.[75] Digital cyanosis with cold exposure is a classic presentation, and evidence of cold-induced paroxysmal hemolytic anemia may also be present. The first-line treatment for disorders of cryogelling is avoidance of cold and treatment of underlying disease (i.e. malignancy). Stanozolol has shown some benefit as an adjunctive therapy.[76]

Figure 3.

Cryoglobulinemia.

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