Pearls from the Scope—What Your Dermatopathologist Wants You to Know: Direct Immunofluorescence

J Clin Aesthet Dermatol. 2023;16(12 Suppl 2):S33–S35

by Maria R. Robinson, MD, MBA, FAAD

Dr. Robinson is a board-certified dermatologist and dermatopathologist with over 15 years of experience across the academic, private practice, and telehealth sectors. She has a passion for education, and is the founder of www.dermpathforapc.com, an innovative online dermatopathology CME course for advanced practice clinicians.  

FUNDING: No funding was provided for this article.

DISCLOSURES: Dr. Robinson reports no conflicts of interest relevant to the content of this article. 

ABSTRACT: Direct immunofluorescence (DIF) is a valuable diagnostic tool in the dermatology clinic. The proper use of a biopsy for DIF is dependent on several factors, including appropriate clinical indication, correct clinical site selection, and proper specimen handling and transport. Improper use of DIF can lead to false negatives, decreased diagnostic yield, and poor resource utilization. This article provides instruction on the appropriate indications and biopsy site selection for DIF. Three examples of skin diseases in which DIF would be particular useful when making a diagnosis are provided.

Direct immunofluorescence (DIF) is a valuable and well-established tool often used in the dermatology clinic. It helps confirm certain diagnoses by detecting the presence of different immune complexes in the skin at various locations, such as the dermo-epidermal junction or dermal blood vessels.^1,2 

Like with other biopsy techniques, the value of DIF is dependent on various factors, such as appropriate indication, site selection, specimen handling and transport, and use in a cost-effective manner.^1–4 When it comes to using DIF in clinic, gaps in clinician knowledge and practice can negatively influence results. This can lead to false negatives, decreased diagnostic yield, poor utilization of resources, and ultimately negatively affect patient care. 

Indications for DIF in dermatology

DIF is valuable when specific skin diseases are being considered in the differential diagnosis (Table 1). Depending on the disease process, DIF findings may be specific and diagnostic or they may be highly characteristic or suggestive of certain skin conditions.⁵ This is why DIF should be used in conjunction with histopathology and a thorough clinical history to improve diagnostic yield.² Notably, DIF is not useful for eczematous dermatitis and its various subtypes. 

Biopsy site selection

When performing a biopsy for DIF, correct site selection is critical for accurate results, and it varies depending on the suspected disease entity.^3,5 Biopsies for DIF and histologic evaluation with hematoxylin & eosin (H&E) are often done at the same patient encounter. Doing this can help expedite the final results, since H&E and DIF correlations are often performed. Additionally, a single visit can be more convenient for the patient.  

Autoimmune blistering diseases

For autoimmune blistering diseases, the biopsy for DIF should be done on perilesional skin (normal looking skin) within 1cm of the bulla. Biopsies from the lower extremity have been associated with a higher likelihood of false-negative results, particularly with bullous pemphigoid. For this reason, this anatomic site should be avoided if possible.³ 

For the H&E biopsy, if the lesion is small, the entire lesion should be removed with a deep saucerization or punch biopsy. For a large bulla, the biopsy should be from the edge of the blister and contain both portions of the blister and intact skin (Figure 1). Both methods provide the dermatopathologist with enough tissue to evaluate the entire depth of the pathologic changes, which results in a more specific diagnosis or differential diagnosis. 

Vasculitis

For vasculitis, the biopsy for DIF should be a punch biopsy or deep shave in the center of a newer lesion (ideally less than 24 hours old). For an H&E biopsy, a punch biopsy or deep shave in the center of a well-established purpuric older lesion is ideal (ideally around 72 hours)(Figure 2).³

Connective tissue disease

For connective tissue disease, such as lupus erythematosus and dermatomyositis, the biopsy for DIF and H&E should both be a punch biopsy of lesional skin that is established and still active (Figure 3). For DIF, the immune deposits are best shown in lesions that are greater than six months old.³ A punch biopsy is preferred over a shave biopsy for evaluation of the deep infiltrate.  

Clinical case review

The following clinical case highlights the correct locations for both DIF and H&E biopsies. A 72-year-old man presented with a widespread, pruritic eruption consisting of numerous erythematous bullae. The biopsy for H&E could be a punch biopsy or deep shave of the edge of an active blister (small blue circle, Figure 4) or of an entire blister (large blue circle, Figure 4). The biopsy for DIF should be a punch biopsy or deep shave of uninvolved perilesional skin within 1cm of a bulla (green circle, Figure 4). 

Specimen handling

After obtaining a biopsy from the appropriate site, correct tissue handling and transport is necessary for optimal and accurate results.  

Biopsy tissue obtained for DIF should be placed in Michel’s or Zeus’s transport medium for preservation and transport. If these are not available, specimens transported on normal saline-soaked gauze can be used with two caveats: the laboratory must accept this type of specimen, and the specimen has to be delivered within 24 to 48 hours. Specimens transported in Michel’s medium can stay at room temperature for at least two weeks without loss of signal.^1,3

At times, DIF specimens are inadvertently placed into formalin for transport. If this happens, the tissue may be retrievable depending on the suspected disease and the amount of time in the formalin. For example, pemphigus will have negative results even with a brief exposure to formalin (2 minutes). However, bullous pemphigoid and dermatitis herpetiformis can survive up to 10 minutes without disrupting the signal. Occasionally, a regular biopsy specimen for H&E is mistakenly placed in Michel’s medium for transport. In this situation, the tissue can simply be transferred into formalin without affecting the tissue’s quality or preservation.¹

Conclusion

In the right clinical context and with the proper clinical site selection, biopsy technique, and specimen handling, DIF is an important diagnostic tool available to clinicians. If the submitting clinician has any questions about these contributing factors or the pathology report, they should not hesitate to call the dermatopathologist for discussion and further clarification. 

References

1. Kim RH and Brinster NK. Practical direct immunofluorescence. Am J Dermatopathol. 2020 42:75–85. 
2. Minz RW, Chhabra S, Singh S, et al. Direct immunofluorescence of skin biopsy: perspective of an immunopathologist. Indian J Dermatol Venereol Leprol. 2010 76:150–157. 
3. Elston DM, Stratman EJ, Miller SJ. Skin biopsy: biopsy issues in specific diseases. J Am Acad Dermatol. 2016 74:1-16.
4. Reimann JD, Moynihian SP, Horn TD. Assessment of clinical and laboratory use of the cutaneous direct immunofluorescence assay. JAMA Dermatol. 2021 157:1343–1348. 
5. Chhabra S, Walker Minz R, Saikia B. Immunofluorescence in dermatology. Indian J Dermatol Venereol Leprol. 2012 78:677–691.