Alarm reaction of pilosebaceous apparatus Amir H. Mehregan, M.D. Monroe, MI A series of histologic changes involving the pilosebaceous structures are described under the term "alarm reaction." The follicular manifestation of this phenomenon is characterized by regression of hair matrix, forming a well-defined nest of small basaloid tells tbund in various parts of the follicular canal. The sebaceous glands either become undifferentiated, forming a solid mass of stratified squamous epithelium, or the sebaceous Iobules are taken into the follicular canal and into the surface keratin layer. (J AM ACAD DERMATOL 1:55-58, 1979.)
An interesting phenomenon is reported observed in the histologic examination of skin specimens involving the small body and facial hair follicles. This phenomenon is characterized by regression of the hair matrix epithelium into a solid nest of undifferentiated basaloid cells. This nest of cells is eventually taken into the follicular canal and is gradually moved into the surface epidermis. This phenomenon can be explained best as an alarm reaction of the small hair follicles. MATERIAL Clinicopathologic data on fifteen instances studied are summarized in Table I. Skin tissue specimens examined were fi'om individuals ranging between 20 and 64 years of age, There were nine women and six men. The specimens consisted of four of facial skin, six of skin of the upper extremities, and five of the trunk. In eight instances, the lesion excised was a neoplasm. In the other seven instances, the histologic findings were inflammatory or dermatitic. The tissue sections were stained by hematoxylin-eosin and by acid orceinGiemsa techniques. From the Pinkus Dermatopathology Laboratory. Reprint requests to: Dr. A. H. Mehregan, Pinkus Dermatopathology Laboratory, 1314 N. Macomb, P.O. Box 360, Monroe, MI 48161. 0190-9622179/010055+04500.40/0 9 1979 Am Acad Dermatol
HISTOLOGIC FINDINGS Follicular changes involved both the small body hairs and the lanugo-type facial hair follicles. From one to as much as three involved hair follicles were present in one specimen. The involved hair follicles showed regression of the hair matrix epithelium transformed into a well-defined nest of basaloid cells moved up into the follicular canal (Figs. 1 and 2). The basaloid cells forming the solid nest are elongated in the direction of the hair follicle. The intrafollicular nest of basaloid cells is often separated from the surrounding follicular epithelium by empty clefts or shrinkage spaces (Fig. 3). The nests of basaloid cells are found within various levels of the follicular canal and are eventually moved into the surface keratin layer (Fig. 4). Occasionally, a small and nonpigmented hair shaft is present within the nest of basaloid cells, confirming its hair matrix origin (Fig. 5). COMMENTS Alarm reaction is a phenomenon that is known to affect sebaceous glands in various inflammatory dermatoses. 1 One histologic manifestation of the alarm reaction is characterized by regression and transformation of the sebaceous lobules into masses of stratified squamous epithelium (Fig. 6). Failure of sebaceous maturation and replacement by undifferentiated epithelial cells in various 55
Journal of the American Academy of Dermatology
Fig. 1. R e g r e s s i o n of the hail" matrix epithelium is char-
Fig. 2. The nest of basaloid cells is moved up into the
acterized by f o r m a t i o n o f a solid nest o f basaloid ceils at the lower pole o f the follicle.
follicular sheath epithelium.
Table I. C l i n i c o p a t h o l o g i c d a t a
No. I Age Sex [Race [
Clinical diagnosis lntradermal nevus Actinic keratosis N u m m u l a r eczema Verruca vulgaris Intradermal nevus Basal cell epithelioma Basal cell epithelioma Asteatotic dermatitis Contact dermatitis Intradermal nevus Pigmented basal cell epithelioma L i c h e n simplex chronicus Discoid lupus erythematosus Psoriasis Asteatotic dermatitis
1 2 3 4 5 6 7 8 9 10 11
64 39 62 48 2I 20 6t 20 26 26 24
F M F F F F F M M F M
W W W W W W W W W W W
U p p e r lip Wrist U p p e r arm Chin Back Face Face Forearm Chest Arm Back
12 13 14 15
30 59 30 35
F M F M
W W W W
Forearm Chest Chest Arm
Histologicdiagnosis Intradermal nevus Actinic keratosis NummuIar eczema Verruca vulgaris Compound nevus Fibroma Granuloma fissuratum Asteatotic dermatitis Contact dermatitis Compound nevus Malignant melanoma Lichen simplex chronicus Discoid lupus erythematosus Psoriasis Asteatotic dermatitis
Volume 1 Number 1 July, 1979
Pilosebaceous alarm reaction
Fig. 3. The nest of basaloid cells is well defined and is separated i-tom the surrounding follicular sheath epithelium by an empty cleft.
Fig. 4. GradtJally the nest of basaloid cells is moved into the surface keratin layer.
Fig. 5. The regressed hair matrix often shows a central small hair shaft.
Fig. 6. Alarm reaction is characterized by transformation of a sebaceous lobule into a solid mass of stratified squamotJs epithelium.
Fig. 7. Shows intrafollicular disposition of sebaceous
pathologic c o n d i t i o n s w e r e well investigated b y Strauss a n d K l i g m a n in 1958. 2 I n a n o t h e r manifestation, the s e b a c e o u s lobules are t a k e n into the follicular canal and are g r a d u a l l y m o v e d into the surface keratin l a y e r (Figs. 7 a n d 8). 1 This latter p r o c e s s is o c c a s i o n a l l y o b s e r v e d in the routine e x a m i n a t i o n o f the histologic sections o f facial skin e v e n in the a b s e n c e o f inflammation. 3"'1 It has also b e e n o b s e r v e d in the p r o c e s s o f w o u n d healing. ~ T h e process d e s c r i b e d in this article a p p e a r s to be of similar n a t u r e , involving the small hair follicles. It begins with cessation o f hair f o r m a t i o n and regression of t h e hair matrix epithelium into a nest o f basaloid cells. The n e s t is t a k e n in and is gradually m o v e d up into the follicular canal. In s e v e n instances, the follicular c h a n g e s o c c u r r e d within the areas of d e r m a t i t i s a n d in a s s o c i a t i o n with inflammation. In eight o t h e r instances, h o w e v e r , the follictdar c h a n g e s w e r e f o u n d i n d e p e n d e n t o f
Journal of the American Academy of Dermatology
Fig. 8. Shows a small Sebaceous lobule moved into the surface opening of the hair follicle.
inflammation within or in the vicinity o f a cut a n e o u s n e o p l a s m . Further investigation is needed to clarify the role of inflammation or other factors such as t r a u m a in the initiation o f this f o r m of follicular reaction. REFERENCES I. Pinkus H, Mehregan AH: A guide to dermatohistopathology, ed. 2, New York, 1976, Appleton-Century-Crofts. 2. Strauss JS, Kligman AM: Pathologic pattern of the sebaceous gland. J Invest Dermatol 30:51-61, 1958. 3. Weigand DA: Transfollicular extrusion of sebaceous glands: Natural phenomenon or artifact? A case report. J Cutan Pathol 3:239-244, 1976. 4. Hoffmann E: Ober Retention von Talgdrtisensekret mit Erhaltung des Zelligen Charakters innerhalb der Hornschicht. Arch fur Dermat u Syph 64:1-15, 1903. 5. Eisen AZ, Holyoke JB, Lobitz WC Jr: Responses of the superficial portion of the human pilosebaceous apparatus to controlled injury. J Invest Dermatol 25:145-156, 1955.