A Male with Acute Dermonecrosis over the Right Flank

A 42-year-old farmer presented with an acute onset painful red raised lesion over the right side of his abdomen. While working in the paddy fields, the patient experienced a spider bite 3 days before the onset of this complaint. Initially, he had pain for a day, followed by redness and blister formation that eventually ruptured. He did not have any systemic complaints. On cutaneous examination, he had a single necrotic boggy plaque over the right flank. A linear streak of erythema was noted emanating from the superior aspect of the ovoid lesion [Figure 1a]. Dermoscopy showed a central bluish-black crust outlined by an irregular non-homogeneous reddish blue area in an erythematous background [Figure 2]. There was no regional lymphadenopathy.Figure 1: (a) A single oval erythematous boggy plaque of size 9 cm × 7 cm with a central necrosis over the right flank, with a linear streak of erythema emanating from the superior aspect of the ovoid lesion; (b-f) Follow-up on day 5, day 10, day 16, day 30, and day 52Figure 2: A central bluish-black crust outlined by an irregular non-homogeneous reddish blue area in an erythematous backgroundThe vital parameters, hemogram, liver function tests, renal function tests, bleeding time, and clotting time were found to be normal. What is the diagnosis? Answer: Cutaneous loxoscelism with dermonecrosis Discussion The diagnosis of cutaneous arachnidism (loxoscelism) with dermonecrosis was made based on the positive history of spider bite, clinical presentation, and dermoscopy. The patient was managed with topical collagenase ointment, oral acetaminophen, a prophylactic antibiotic with intravenous ceftazidime twice daily, and oral prednisolone 0.4 mg/kg/day for 7 days. The patient was periodically followed up [Figures 1b-f]. The lesion healed with a hypertrophic scar. Necrotic arachnidism is a cutaneous reaction to toxins released from the venoms of spider bites. Loxoscelism is a term used for spider bites associated with loxosceles species.[1] Cutaneous loxoscelism is the most common presentation of loxoscelism. Systemic involvement with fever, myalgia, and hemolytic anemia can rarely occur.[1] The differences between cutaneous and systemic loxoscelism are mentioned in Table 1.[2] The toxins responsible for cutaneous loxoscelism are enzymes sphingomyelinase-D, phospholipase-D, alkaline phosphatase, hyaluronidase, esterase, and proteases.Table 1: Differences between cutaneous and systemic loxoscelism.Clinically cutaneous loxoscelism presents as a painful localized bluish-gray halo surrounding the bite site. This is followed by a vesicle or cyanotic pustule with surrounding erythema, edema, and purpura. Later, a central ischemic pallor with a dry, crusted, necrotic lesion with surrounding erythema, vesiculation, and pustulation is noted. The lesion spreads rapidly and extensively, with the eschar shedding and leaving erosions and ulcers. The affected site may take up to 6 months to heal with or without scarring. The pathognomic lesional description is a classical red, white, and blue sign. The red depicts erythema, followed by a palisaded white ring of vasoconstriction due to the toxin, and a central blue necrotic zone.[1] The most common affected sites are the proximal part of the lower extremity and the distal part of the upper extremity. Lymphedema can occur as a complication to loxoscelism.[3] The conditions that mimic cutaneous loxoscelism are arthropod bites, erysipelas, ecthyma, cellulitis, urticaria and angioedema, burns, vasculitis, pyoderma gangrenosum, cutaneous diphtheroid, anthrax, and cutaneous malignancies.[4,5] There are no standard guidelines for the management of cutaneous loxoscelism. Spider bites generally require rest to the involved part, analgesia, sterile dressing, and periodic follow-up. Cutaneous loxoscelism with dermonecrosis may require systemic steroids, prophylactic antibiotics, vasodilators, dapsone, tetracycline, heparin, and hyperbaric oxygen therapy.[4,6] Systemic involvement, which develops anytime within 12–36 hours after the bite, requires vigorous hemodynamic management.[2] Antivenin provides beneficial effects like prevention of necrosis, edema, and ecchymoses when administered as early as possible.[7] A high index of suspicion should be kept in mind to diagnose this entity in patients presenting with acute onset ulceration. A proper history taking and clinical examination holds the key to clinching the diagnosis. The aim of reporting this case is to emphasize the clinical evolution of cutaneous loxoscelism, which may pose a diagnostic dilemma. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.