When An Elderly Patient Presents With A Painful Blister And Swelling

By M. Joel Morse, DPM

   A fat-soluble vitamin, vitamin K, is an essential component in the production of many of the coagulation proteins. An alteration in the synthesis of vitamin K-dependent coagulation factors is usually reflected by changes in the PT and INR.2

   Many antibiotics alter the balance of gut flora, thereby enhancing the effect of warfarin. In the gut, bacteria would normally produce vitamin K but when less bacteria do not produce the vitamin K, the vitamin K dependent clotting factors (factors 2, 5, 9 and 10) are affected. Also note that older patients who may not be eating well and have poor nutritional habits may already have a deficiency of vitamin K.

   An increased INR secondary to warfarin interactions with various antibacterial agents is a known phenomenon. An increased awareness of warfarin–antibiotic interaction and appropriate monitoring is essential to control the INR levels and prevent bleeding complications. 4

A Guide To The Differential Diagnosis

   Spider bite. Insect and spider bites often cause minor swelling, redness, pain and itching. These mild reactions are common and may last from a few hours to a few days. In this case, once I ruled in the hematoma, I ruled out a spider bite.

   Insect bite. Insect bites may be grouped, popular or urticarial, and have a surrounding halo. Occasionally one can see a central depression. Some insect bites result in a hemorrhagic bullae. Bullae formation and tissue necrosis are more common with spider bites but may also be caused by insect bites. This patient had a bullae that was not hemorrhagic. This finding initially had me thinking this was due to an insect or spider bite.

   Cellulitis. This is a common infection of the dermis and the subcutaneous tissues caused by a bacterial infection. It can arise without an obvious source for the bacterial infection. Staphylococci are the bacteria that most commonly cause cellulitis. Streptococci is the next most common cause.

   Cellulitis usually begins as a small area of pain and redness on the skin. This area spreads to surrounding tissues, resulting in the typical signs of inflammation: redness, swelling, warmth and pain. One can also develop fever and/or swollen lymph nodes in the area of the infection. This patient has a negative culture and a lack of warmth to the area.

   Trauma. Trauma can cause various types of bleeding into tissues. It is the primary cause for hematomas. Occasionally after an injury, blood collects and pools under the skin, resulting in a hematoma and giving the skin a spongy, rubbery, lumpy feel. A regular bruise is more spread out and may not feel like a firm lump. When there is trauma, an X-ray is normally required to aid in the diagnosis.

   Drug induced purpura. These are primarily found on the feet and ankles (dependent areas).

   Drug reaction. Drug reactions can mimic a wide range of dermatoses. The morphologies are myriad and include morbilliform, urticarial, papulosquamous, pustular and bullous. Medications can also cause pruritus and dysesthesia without an obvious eruption. One should consider the possibility of a drug-induced reaction in any patient who is taking medications and who suddenly develops a symmetric cutaneous eruption.

   In this patient, the rash was only on the top of the foot and there was no pruritus. Severe dermatologic reaction as a result of drug side effects usually manifests in multiple blisters whereas this patient just had a single blister.

How To Treat A Hematoma

   In general, the quicker one applies ice after the injury, the less bleeding will result. If possible, elevate the bruised limb, which may lead to less swelling. Resting the limb will also help to prevent further injury.

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