Figure 2.1
Tense inflammatory blister in a patient with bullous pemphigoid
Her clinical presentation, coupled with microscopic and immunologic data, supported a diagnosis of bullous pemphigoid (BP). Suffering from degenerative joint disease and living independently, the patient felt unable to apply topical corticosteroids, particularly given the widespread distribution of her lesions. Therefore, she was started on prednisone 1 mg/kg/day and mycophenolate mofetil. Being intolerant of the latter medication, she was then started on minocycline and niacinamide in lieu. In anticipation of long-term corticosteroid use, she was counseled by her dermatologist and primary care physician to take supplemental calcium, vitamin D, a bisphosphonate, trimethoprim-sulfamethoxazole for Pneumocystis jiroveci pneumonia (PCP) prophylaxis, and a proton-pump inhibitor. Given her comorbid diabetes mellitus, she was also advised to check her blood glucose levels frequently. After 3 weeks of immunosuppressive therapy, she reported marked improvement in her BP. Over the ensuing weeks, her prednisone dose was tapered.
Three months later, a flare of her BP prompted an increase of her prednisone dose back to 1 mg/kg/day. Shortly thereafter, she presented to the emergency department with altered mental status. Urinalysis showed elevated urinary ketones and glucose without bacteria, leukocyte esterase, or nitrites.
The most likely diagnosis is:
(A)
Acute-onset of Alzheimer dementia, a neurologic condition associated with bullous pemphigoid
(B)
Progressive multifocal leukoencephalopathy, an opportunistic infection by the JC virus
(C)
Urinary tract infection, a common cause of confusion in the elderly
(D)
Hyperglycemia, exacerbated by the patient’s recently increased prednisone dose
Diagnosis
Hyperosmolar hyperglycemia in the setting of systemic corticosteroid therapy for bullous pemphigoid
Discussion
The patient’s serum glucose level was found to exceed 600 mg/dL, confirming a diagnosis of hyperosmolar hyperglycemia. Her family revealed that she had become confused since her prednisone dose had increased, and she had not been diligent about checking her serum glucose at home. Following hospitalization for medical stabilization, and after confirming a normal serum thiopurine methyltransferase level, she was started on azathioprine and her prednisone dose was tapered to 5 mg/day. She has done well after 2 years of follow-up.
Bullous pemphigoid is a common autoimmune blistering disease associated with the development of autoantibodies against BP180 and BP230 antigens of the basement membrane zone. Although considerable evidence supports the use of topical corticosteroids in this condition [1, 2], logistical barriers associated with applying topical medications to widespread areas of the body in this often elderly population may necessitate the use of systemic corticosteroids to achieve rapid disease control in patients with widespread disease [3]. Although this patient had received high-dose prednisone, the best available evidence indicates that higher dose regimens of systemic corticosteroids offer no therapeutic benefit over lower dose regimens [4, 5]. Exposure to systemic corticosteroids should be minimized given their adverse side effect profile. Specific risks associated with systemic corticosteroids include hyperglycemia, osteopenia, delirium, osteonecrosis of the hip, Pneumocystis jiroveci pneumonia and other opportunistic infections, cataracts, redistribution of body fat, myopathy, gastric ulcers, and striae [6, 7]. Caused by reactivation of the JC virus, progressive multifocal leukoencephalopathy has been anecdotally reported to occur with prednisone use [8] but is more frequently observed as a complication of rituximab or efalizumab. Since systemic corticosteroid therapy can be prolonged in patients with BP, it is necessary to regularly look for opportunities to lower the dose, to closely monitor blood glucose in patients with glucose intolerance or frank diabetes mellitus and to address bone health, gastric protection, and Pneumocystis prophylaxis.
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