AGA or LPP: Who is right?

In many fields of medicine, the pathology report provides the final answer as to a patient's diagnosis. We're most familiar with this for example with cancer diagnoses. It comes as a surprise for many patients that scalp biopsy reports are sometimes not so definitive.

Differentiating AGA and LPP

A great example is the diagnosis of early androgenetic alopecia (AGA and early lichen planopilaris (LPP). Sometimes it is pretty clear cut - but not always. Sometimes a diagnosis of LPP is made and the patient really has AGA. Sometimes (although much less commonly) a diagnosis of AGA is made and the patient really has LPP.

LPP: Brief Overview

Lichen planopilaris (LPP) is a scarring alopecia that typically starts with scalp symptoms such as itching and burning. Sometimes the scalp is quite tender in areas. Shedding is often present as well. LPP affects similar areas to androgenetic alopecia (female pattern thinning) so it is a close mimicker. In the early stages, some scalp redness may be present and inflammation may be seen around the hairs clinically. 

AGA: Brief Overview

Androgenetic alopecia (AGA) also starts with shedding. There can be a hint of itching/tingling but not too often. Usually the front of the scalp is more affected by hair loss than the back. 

Biopsies: Helpful or not?

A biopsy can be very helpful provided it is read by an experienced dermatopathologist. Traditionally we have thought of AGA as "non inflammatory" and "non scarring" so one might not think that inflammation and scarring should be present on the biopsy. We know now that's not completely true.  Inflammatory infiltrates are present in AGA in the upper hair follicle and so is loose perifollicular fibrosis. In LPP biopsies, inflammation is also present in the upper hair follicle but it specifically appears to be attacking the hair follicle outer root sheath. (We call this "lichenoid" change). To differentiate AGA and LPP one needs to direct their attention to this specific change in the actual hair follicle. When this specific immune attack is seen, one needs to consider LPP over AGA. Also the amount of perifollicular fibrosis is usually greater as LPP advances. LPP may have other changes in the skin as well that help differentiate it from AGA.

So by biopsy,  androgenetic alopecia and LPP can be confused as both can have inflammation (perifollicular inflammation in the isthmus) and both can have scarring (perifollicular fibrosis).  An experienced dermatopathologist can sort this out. 

So how does one resolve this? Does the patient have AGA or LPP?

One needs to take into account the patient's entire story. If a physician just biopsies every patient that comes into the office, I can guarantee one will make a whole lot more diagnoses of LPP than truly are present. I'm a big believer in this - even though LPP is under diagnosed in the world!  But by listening to the patient's entire story, and examining the scalp and reviewing what the biopsy shows (not just the final read out on the bottom line), one can usually get a fairly good sense. However in rare cases - time is the best judge as a missed case of LPP will likely declare itself over time.