|Year : 2014 | Volume
| Issue : 1 | Page : 21-24
Association of the cornoid lamella with the follicular infundibulum and the acrosyringium: A histological analysis
Mary Thomas, Uday S Khopkar
Department of Dermatology, King Edward Memorial Hospital and Seth Gordhandas Sunderdas Medical College, Parel, Mumbai, Maharashtra, India
|Date of Web Publication||24-Jun-2014|
Department of Dermatology, St. Johns Hospital, Bangalore - 560 034, Karnataka
Source of Support: None, Conflict of Interest: None
Background: The classical histological feature of porokeratosis (PK) is the cornoid lamella. The occurrence of the cornoid lamella within the follicular infundibulum and the acrosyringium is believed to be primarily associated with specific types of PK, for example, follicular PK, porokeratotic eccrine and hair follicle nevus. We looked for such occurrence in all cases of PK. Objective: We attempted to evaluate the incidence of follicular and acrosyringeal involvement in the various clinical types of PK in our population and describe the histological features of the same. Materials and Methods: Case records in 2011 were reviewed for patients diagnosed with PK based on clinicopathological correlation. The histology was reevaluated and follicular or acrosyringeal involvement was noted. Results: In total, biopsies from 28 lesions from 16 patients were reviewed. Nine (32%) lesions were found to have follicular involvement and 12 (42%) were found to have acrosyringeal involvement on histopathology. Of these, 61% of these patients were clinically diagnosed as PK of Mibelli (PM), 14% as disseminated superficial actinic PK (DSAP), 13% as linear PK (LP), 7% cases of follicular PK (FP), and 7% as genital PK. Conclusions: Follicular and acrosyringeal involvement in PK is more frequent than expected. Though follicular PK has been described as a distinct entity, there is no correlation between the clinical subtype and the involvement of the follicular infundibulum and acrosyringium. This involvement may occur as an incidental finding and hence, histological delineation of follicular or acrosyringeal PK as distinct entities without appropriate clinical correlation appears unjustified.
Keywords: Follicular, porokeratosis, porokeratotic eccrine and hair follicle nevus
|How to cite this article:|
Thomas M, Khopkar US. Association of the cornoid lamella with the follicular infundibulum and the acrosyringium: A histological analysis. Indian J Dermatopathol Diagn Dermatol 2014;1:21-4
|How to cite this URL:|
Thomas M, Khopkar US. Association of the cornoid lamella with the follicular infundibulum and the acrosyringium: A histological analysis. Indian J Dermatopathol Diagn Dermatol [serial online] 2014 [cited 2019 Feb 17];1:21-4. Available from: http://www.ijdpdd.com/text.asp?2014/1/1/21/135192
| Introduction|| |
Porokeratosis (PK) is a disorder of keratinization characterized by annular plaques with normal or atrophic centers surrounded by a keratotic ridge [Figure 1]. Histologically, this ridge corresponds to the cornoid lamella.  It was first described by Mibelli in 1889 and since then many other clinical variants have been described.  The recognized common clinical variants of PK include PK of Mibelli (PM), disseminated superficial actinic PK (DSAP), linear PK (LP), PK plantaris palmaris et disseminata, and punctuate PK.  Earlier it was assumed that PK originates from the eccrine ostium, yet acrosyringeal and follicular involvement were considered to be relatively rare.  Such involvement has been often discussed in conjunction with certain types, for example, follicular PK (FP),  porokeratotic eccrine ostial and dermal duct nevus particularly in a rare variant, the porokeratotic eccrine and hair follicle nevus (PEHFN).  We describe the incidence of follicular involvement across the spectrum of PK in our population and describe the clinical and histological features of the same.
|Figure 1: Porokeratosis of Mibelli: A classical lesion showing an annular plaque with normal or atrophic centers surrounded by a keratotic ridge|
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| Materials and Methods|| |
The study was conducted in a tertiary care hospital in India. We studied all cases of PK diagnosed clinically that presented to our hospital over a period of 1 year. The clinical details, type of PK and histopathological features were reviewed and the presence of follicular and acrosyringeal involvement was documented. Multiple sections of each specimen were analyzed and the presence of cornoid lamellae associated with the follicular infundibulum of the acrosyringium were noted.
| Results|| |
In total, 28 lesions from 16 patients were analyzed. The age of the patients ranged from 16-48 years (mean age: 32 years).
The clinical spectrum of the lesions that were biopsied is described in [Figure 2]. The follicular and acrosyringeal involvement in the various types of PK evaluated in this study are described in [Figure 3],[Figure 4],[Figure 5] and [Figure 6].
|Figure 2: Clinical spectrum of porokeratoses evaluated in the study PM = Porokeratoses of Mibelli, DSAP = disseminated actinic superfi cial porokeratosis, LP = linear porokeratosis, FP = follicular porokeratosis, GP = genital porokeratosis|
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|Figure 3: Follicular involvement in porokeratosis: Cornoid lamella arising from the lower third of the follicular infundibulum|
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|Figure 4: Follicular involvement in the various types of porokeratosis. PM = Porokeratoses of Mibelli, DSAP = disseminated actinic superficial porokeratosis, LP = linear porokeratosis, FP = follicular porokeratosis, GP = genital porokeratosis|
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|Figure 6: Acrosyringeal involvement in various types of porokeratosis PM = Porokeratoses of Mibelli, DSAP = disseminated actinic superficial porokeratosis, LP = linear porokeratosis, FP = follicular porokeratosis, GP = genital porokeratosis|
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The follicular involvement was seen as parakeratotic columns arising from the lower third of the follicular infundibulum overlying an absent granular layer, dyskeratotic cells, and occasional vacuolar degeneration of the basal layer. The acrosyringeal involvement was seen as cornoid lamellae within dilated eccrine ostia.
In all cases, except in FP, cornoid lamellae independent of the follicular infundibulum and eccrine ostia were also noted.
| Discussion|| |
PK comprises a diverse group of disorders characterized clinically by marginate scaly lesions with a peripheral keratotic ridge that histologically corresponds to the cornoid lamella. The cornoid lamella is classically described as an area of stacked parakeratosis within a keratinous invagination in the epidermis, which is angled towards the center of the lesion. The underlying granular layer is usually decreased or lost. 
In 1883, Mibelli named PK based on the assumption that columns of parakeratosis emerge from the ostia of the eccrine ducts.  In the same year, Respighi emphasized the plugging of the follicle and the acrosyringium in PK. 
There is very limited literature evaluating the involvement of the follicular infundibulum and acrosyringium across the clinical spectrum of PK. PK involving the follicle has been described in FP, ,, DSAP, , LP,  and PM; , although, the incidence is thought to be rare. PK involving the hair follicle and eccrine ostia exclusively has also been described in PEHFN which presents as multiple, asymptomatic, linear, hyperkeratotic plaques classically involving bilaterally the distal part of the extremities. It is seen in full-term newborns. ,,
In one retrospective study, of the 86 lesions biopsied, 21 had follicular involvement and 16 had acrosyringeal involvement. No correlation was noted between the subtypes.  These results are similar to our study.
The pathogenesis of PK and the mechanism(s) of its abnormal keratinization are still unknown. Recent studies show that an abnormal mutant clone of keratinocytes expands peripherally, leading to the formation of cornoid lamella at the boundary between the clonal population and the normal epidermal cells. A gene located on 12q23.2-q24.1 might play a key role in the abnormal nature of these cells. 
It has been hypothesized that the expanding clone of abnormal keratinocytes is perceived by the immune system (Langerhans cells) as foreign and presented to T cells, which attack this abnormal clone leading to lichenoid reaction similar to lichen planus. However, since this abnormal focus keeps healing and spreading at the same time, the lichenoid lesion enlarges towards the periphery clinically forming a ring. 
Earlier theories suggest that it is a disorder of the eccrine sweat glands. It has been proposed that the invagination of the epidermis may result from an abnormal clone of epidermal cells which leads to the formation of cornoid lamella. Another hypothesis suggests that the invagination is a dilated acrosyringeal and dermal duct which is keratin-plugged. 
The abnormal epidermal cell clones are thought to form parakeratotic columns at the boundary of epidermal appendages in the presence of intact stem cells of hair follicles and sweat ducts.  The occurrence of the cornoid lamella in the lower parts of the follicular infundibulum and acrosyringium observed in our study support this hypothesis.
Hence, the follicular and acrosyringeal involvement occurring in a number of cases across the clinical spectrum of PK is not surprising. A dermatopathologist must be aware of this finding and correlate with the clinical features before diagnosing follicular PK or PEHFN.
| Conclusion|| |
We believe that the follicular and acrosyringeal involvement in PK is not restricted to a distinct entity and may occur across the spectrum of PK. Clinicopathological correlation is essential prior to diagnosing follicular PK and PEHFN.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]