The Diagnosis: Acquired Acrodermatitis Enteropathica
Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,1 eating disorders,2 bariatric and other gastrointestinal surgeries,3 malabsorptive diseases,4 and nephrotic syndrome.5
Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.6 Zinc is found in most foods, but animal protein contains higher concentrations (Table).7 Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.8 Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.
Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.9 Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.9
Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.9 Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis10 (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.
Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.9 Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.11 Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.
Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.12 Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.
Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.