Are sebaceous glands atrophied in seborrheic dermatitis too?

Sebaceous Gland Atrophy is seen in Seborrheic Dermatitis - not just Psoriasis

Authors of a new study set out to determine if biopsies of seborrheic dermatitis showed sebaceous gland (SG) atrophy. In other words, are sebaceous glands smaller and more immature in SD than would be found in the normal scalp?

SG atrophy is well known amongst pathologists to be found in scalp psoriasis. When pathologists see atrophy of the sebaceous glands they often propose that psoriasis may be present. Of course, when sebaceous glands are absent altogether a whole new group of conditions - known as scarring alopecias - need to be considered. Changes in SGs have been well-documented in scalp lesions of psoriasis. Psoriasis that is associated with hair loss and scalp psoriasis not associated with hair loss both can be associated with loss of sebaceous glands. SG atrophy associated with hair loss in the setting of psoriasis is referred to as “psoriatic alopecia”. In 1989, It was Dr David Headington and colleagues who first reported the occurrence of SG atrophy in patients with psoriasis Since then, pathologists haven been on the look out when biopsies of hair loss come in with atrophy of SG.

Nagrani et al 2022

Authors conducted a retrospective study of biopsies fo seborrheic dermatitis.

SGs were considered immature if there was a decrease in size as well as a decrease in central lipidized sebocytes. The maximum SG width in a plane parallel to the epidermis, chosen from multiple sections of three slides cut per specimen, was recorded. Normal SG size was estimated by measuring the maximum SG size in a control group of six cases of inflammatory dermatoses.

Authors found that SG lobules were smaller and narrower (decreased in SG diameter) in 5 of 6 cases of SD. SG atrophy (immature SG) was seen in 4 of 6 cases. The normal size of the SG in control biopsies was higher and ranged from 0.25 to 0.35 mm

Conclusions

The main conclusion fo the study was that SG atrophy is not specific for psoriasis or psoriatic alopecia and is found in SD too. The cause of SG atrophy in psoriasis and seborrheic dermatitis is unclear, but has been attributed to the complex cytokine milieu produced by Type 1 T helper cells including tumor necrosis factor-α, interferon-γ, interleukin-2, and others Psoriasis and seborrheic dermatitis share much in common and are often view as close cousins rather than distant entities. Sometimes, the two are really indistingushable and the term ‘sebopsoriasis’ is used to describe the entity.

SG atrophy is challenging for pathologists and some really challenging cases I see rest of what the pathologists feels about the sebaceous gland. In cases of SG atrophy without good evidence for scarring alopecia, most pathologists write on their final report that the ‘findings could be consistent with psoriasis and/or psoriatic alopecia.” This study reminds us that seborrheic dermatitis is indeed on that list too. Other causes of sebaceous gland atrophy including frontal fibrosing alopecia and other evolving scarring processes always need to be considered.

REFERENCE

Nagrani NS, Goldberg LJ. Sebaceous gland atrophy in seborrheic dermatitis of the scalp; a pilot study.J Cutan Pathol. 2022 Nov;49(11):988-992.

Headington JT, Gupta AK, Goldfarb MT, et al. A morphometric and histologic study of the scalp in psoriasis. Paradoxical sebaceous gland atrophy and decreased hair shaft diameters without alopecia. Arch Dermatol. 1989;125:639-642.