A rash on a woman who rides horses in the winter

Deep punch biopsies were performed and histologic analyses were consistent with a diagnosis of equestrian cold panniculitis, also known as equestrian perniosis (EP). EP involves inflammation of cutaneous and fatty tissue in response to exposure to cold temperatures.1,2 Although the...

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Deep punch biopsies were performed and histologic analyses were consistent with a diagnosis of equestrian cold panniculitis, also known as equestrian perniosis (EP).

EP involves inflammation of cutaneous and fatty tissue in response to exposure to cold temperatures.^1,2 Although the pathogenesis and etiology of the disease is uncertain, EP can present as an idiopathic dermatosis or with an underlying autoimmune disease.¹ It has been described as a cold injury that particularly affects the fatty region of the lateral thighs and hips.³

The condition was first described in 1980 by Beacham et al,⁴ observing young, overweight women wearing poorly insulated and tight-fitting pants during the winter while riding horses for more than 2 consecutive hours. Men do not appear to be affected by EP.⁵ It is a rare phenomenon observed primarily in young women who ride horses.

Patients who do not ride horses and have similar symptoms are diagnosed with a localized form of vasculitis called chilblains, which usually occur on acral skin.^1,3,6 Cases of chilblains have been reported in children wearing wet boots, hikers wading through rivers, cyclists, people who deliver milk, and golf cart drivers.^3,6 According to Yang et al¹ and Boada et al,² all reported cases of EP found in the literature originate in regions with a cold, humid climate.

Cold agglutinins were detected in two patients with EP and persisted with repeat testing over 6 months.⁵ High titers of cold agglutinins could attribute to the persistence of EP skin lesions.⁵ Cold agglutinins are immunoglobulins that are circulating in the blood and cause clumping of erythrocytes. They are thought to play a role in an underlying autoimmune hemolytic anemia that could manifest as EP. Cold agglutinins can develop from tight-fitting pants and cold temperatures (not below 0°C) and are attributed to declining circulation through subcutaneous fat in peripheral areas.⁶ Heavy smoking has also been associated with EP skin symptoms.⁶

Wearing tight clothing may be a contributing factor for the development of equestrian perniosis. A Finnish study found that riders who wore tight-fitting pants all day, instead of only when riding, were at risk of developing skin symptoms.⁶ The epidemiologic survey was performed to determine the prevalence of EP among Finnish horseback riders.⁶ Of the 234 questionnaires sent to members of the Equestrian Federation of Finland, 107 were included in the analysis. There were no other known comorbidities or underlying medical conditions noted, other than the skin lesions. The coldest months of the year in Finland are October through February; one-third of the riders reported symptoms in October, with worsening presentations in January. Demographics, type of work, and skin symptoms were similar to those in the patient presented in our vignette.

Results of a punch biopsy that includes subcutaneous fat can aid in confirmation of the diagnosis of EP, although clinical presentation, riding history, and location of the lesions can provide a clinical diagnosis of the condition.⁶ Differential diagnoses should include cutaneous lupus erythematosus, cutaneous sarcoidosis, and chilblains.² When differentiating chilblains, cutaneous lupus erythematosus, and EP, pathology results will not always confirm the diagnosis. Chilblains and EP have histologic features similar to those of cutaneous lupus erythematosus. Thus, clinical history and distribution of the skin lesions are more conclusive for diagnosis than pathology alone.¹

According to Boada et al,² histopathologic detection of perieccrine distribution in lymphocytic infiltrate is the major identification differentiating between an underlying autoimmune disorder and idiopathic etiology. Routine or expensive blood tests are often not necessary; however, an antinuclear antibody test can aid in distinguishing an underlying autoimmune disorder. Investigating cold agglutinins can contribute to ruling out vasculitis, erythema nodosum, or erythema multiforme.^5,6

Treatment options include wearing warmer clothing, insulating the affected areas more efficiently, and smoking cessation.^5,6 A dihydropyridine calcium channel blocker, nifedipine, is recommended for treatment but has poor evidence supporting therapeutic efficacy. Corticosteroids have been found to help alleviate symptoms; however, there is no one, simple therapy that will prevent or cure EP.⁶

For the patient in our case, deep punch biopsies were performed and sent to two different dermatopathologists for analysis. One biopsy report found superficial and deep perivascular and interstitial lymphocytic infiltrate, whereas the other found perivascular infiltrate composed primarily of small mononuclear cells with infiltration of vessel walls. Both histology explanations are consistent with the diagnosis of EP. After follow-up, the patient stated that topical corticosteroid treatment improved her pruritic symptoms; however, the outside temperature increased in the days following her appointment and she has not yet tried any insulating techniques.

Katie Frisbee, PA, is a physician assistant practicing in family medicine/urgent care, and Alicia Elam, PharmD, is an associate professor in the Physician Assistant Department of Augusta University in Georgia.

References

1. Yang AY, Schwartz L, Divers AK, Sternberg L, Lee JB. Equestrian chilblain: another outdoor recreational hazard. J Cutan Pathol. 2013;40:485-490. 
2. Boada A, Bielsa I, Fernández-Figueras MT, Ferrándiz C. Perniosis: clinical and histopathological analysis. Am J Dermatopathol. 2010;32:19-23. 
3. Weismann K, Larsen FG. Pernio of the hips in young girls wearing tight-fitting jeans with a low waistband. Acta Derm Venereol. 2006;86:558-559. 
4. Beacham BE, Cooper PH, Buchanan CS, Weary PE. Equestrian cold panniculitis in women. Arch Dermatol. 1980;116:1025-1027. 
5. De Silva BD, McLaren K, Doherty VR. Equestrian perniosis associated with cold agglutinins: a novel finding. Clin Exp Dermatol. 2000;25:285-288. 
6. Pekki A, Sauni R, Vaalasti A, Toivio P, Huotari-Orava R, Hasan T. Cold panniculitis in Finnish horse riders. Acta Derm Venereol. 2011;91:463-464.