An illustrated, source-linked reference
A useful skin description starts with what can be observed: a shape, a location, a size and a change over time. This glossary explains words used in Morgellons discussions and skin reports, including comedo-like masses, keratin projections, plugs and casts. It keeps a descriptive label separate from a diagnosis, a material identification and a proposed cause.
Use the word at the level it supports. “Plug-like” is an observation; “keratin” is a material claim; “RPC” is a diagnostic claim. One does not establish the next. This glossary helps organize a conversation with a clinician.
All six diagrams are original schematic teaching drawings, generated from explicitly specified shapes and labels. They are not clinical photographs, microscope images or histologic evidence. They are not to scale and do not reproduce a particular patient specimen. Real color, size and structure vary. See the source papers for their original figures and magnifications.
Find a term
18 terms in three groups. All definitions are visible below.
Morgellons source descriptions
These labels come from two papers by the same research group. Each describes particular specimens in that paper. These source-specific labels are not established diagnostic categories. The two cited papers do not provide independent replication of these particular object descriptions.
Morgellons source description · 2018 review, authors’ unpublished observations
Comedo-like mass
A compact, hardened object that the 2018 review’s authors describe as resembling the contents of a comedone. They report that such masses can emerge from pores on their own or with scratching, that patients sometimes describe them as sand-like, and that some contain embedded or projecting filaments.
What it does not establish: The description appears in a section of the review that the authors base partly on their own unpublished examinations; it reports no counts, methods or composition testing for the masses themselves. “Comedo-like” describes resemblance only. It does not establish acne, composition, infection or how the mass formed, and it is not a validated diagnostic category.
Sources: [3]
Morgellons source description · 2013 specimen study
Keratin projection
In the 2013 specimen study, the authors used this term for projections on the concave underside of removed callus material, the side they describe as facing the dermis. They were most prominent in one of four patients and less so in a second. Some tips were sharp; others were blunt or ballooned. Keratin immunostaining and Gömöri trichrome stained the projections as keratin, and some contained masses of cells that stained positive for collagen.
What it does not establish: The label is source-specific, and its use shifts: the 2018 review from the same group equates keratin projections with “thickened follicular casts.” A similar-looking projection in a new photograph has not thereby been identified as keratin. The study examined detached, non-biopsy material, so neither the paper nor this drawing shows a growth route in intact skin.
Morgellons source description · 2018 review
Follicular cast
The 2018 review states that keratin projections are thickened follicular casts and that, in Gömöri trichrome–stained sections, their outer surface is keratin-rich while the interior can contain collagen-rich tissue. A figure in the same review shows a “filamentous follicular cast” with filaments arising from its outer follicular sheath.
What it does not establish: The passage gives no separate citation, methods or counts; the nearest published staining data are the 2013 callus-projection findings. Specify the author’s usage and the specimen location. Do not transfer the interior-composition claim to ordinary hair casts or to material identified only in a photograph.
Standard lesion and clinical terms
Most of these are defined in the 2016 International League of Dermatological Societies (ILDS) consensus glossary. “Plug” and “hair cast” come from the cited clinical literature instead.
Clinical term · RPC criteria (Faver 1994)
Plug / keratotic plug
“Plug” describes material occupying an opening or a lesion’s center; it is not a defined term in the ILDS glossary. “Keratotic” is the ILDS adjective for hyperkeratosis, a thickened outer cornified layer. Faver and colleagues’ proposed criteria for acquired reactive perforating collagenosis (RPC) include umbilicated papules or nodules with a central adherent keratotic plug. Acne research also describes comedones as containing a plug of cornified material.
What it does not establish: A plug’s appearance alone does not diagnose RPC. The same criteria also require biopsy findings of necrotic collagen eliminated into a cup-shaped epidermal depression, and onset after age 18. Ask whether a clinician means a follicular plug, as in a comedone, or a lesion-centered plug.
Standard term · ILDS 2016
Comedone (comedo)
The ILDS glossary defines comedones by the upper portion of the hair follicle (the infundibulum). In an open comedone (blackhead) it is dilated and holds darkened, oxidized keratinous debris; in a closed comedone (whitehead) it is expanded by keratinous debris, usually with no connection to the skin surface. A 1985 biochemical study found keratin, partly degraded, in material from open acne comedones.
What it does not establish: An ordinary comedone and a reported “comedo-like mass” are different labels. Similar appearance is a reason to examine, not a reason to equate them.
Clinical term · trichoscopy literature
Hair cast / peripilar keratin cast
A sleeve-like structure encircling a hair shaft. In a retrospective trichoscopy study of 42 patients examined for suspected lice, three had hair casts, seen as elongated tubular structures that moved easily along the shaft. The authors note that hair casts are also called peripilar keratin casts.
What it does not establish: Hair casts are one kind of “pseudonit” and can be mistaken for lice eggs or other material on hair. Their presence does not establish lice or Morgellons, and the study did not test their composition. A shaft sleeve is not automatically the same structure as a “thickened follicular cast” in a Morgellons specimen report.
Sources: [5]
Standard term · ILDS 2016
Crust (often called a scab)
Dried serum, blood or pus on the surface of the skin.
What it does not establish: Its presence does not identify the cause of the lesion beneath it. A crust, a plug and a scale describe different features.
Sources: [1]
Standard term · ILDS 2016
Scale
A visible accumulation of keratin forming a flat plate or flake.
What it does not establish: Describe where it lies and whether it is loose or adherent; do not rename every surface particle a fiber or a plug.
Sources: [1]
Standard term · ILDS 2016
Papule
An elevated, solid, palpable lesion no more than 1 cm in diameter in the ILDS nomenclature. The glossary notes that some textbooks use 0.5 cm as the cutoff instead.
What it does not establish: This names a lesion’s form and size, not its cause. Record the measurement rather than relying on a drawing’s apparent size.
Sources: [1]
Standard term · ILDS 2016
Erosion
Loss of part or all of the epidermis, the outer skin layer.
What it does not establish: Depth matters. A photograph may not show it reliably; examination helps distinguish an erosion from an ulcer.
Sources: [1]
Standard term · ILDS 2016
Ulcer
Full-thickness loss of the epidermis plus at least part of the dermis; it may extend into the tissue beneath the skin.
What it does not establish: Describe size, shape, depth, border, base and surrounding skin. “Ulcer” does not establish infection, picking, a perforating disorder or any other cause.
Sources: [1]
Standard term · ILDS 2016
Hyperkeratosis
Thickening of the stratum corneum, the skin’s outermost cornified layer, usually producing a rough surface.
What it does not establish: It is a structural change that occurs in different conditions. It does not identify a specific disease or an extracted object.
Sources: [1]
Standard term · ILDS 2016
Callus
In the ILDS glossary, reactive hyperkeratosis, usually caused by friction or pressure, that accentuates the skin’s surface markings.
What it does not establish: Morgellons specimen papers use “callus” differently, for removed lesion material that the 2018 review says often resembles a scab. Keep that sampling description rather than assuming a friction or pressure callus.
Materials, methods and observation words
These words name a shape, a material or a way of handling a specimen. Each answers a different question from a lesion description or a diagnosis.
Observation word
Fiber / filament
A slender, thread-like structure. The word names a shape, not a material. Morgellons studies have examined different specimen streams: the 2013 study kept only filaments attached to removed tissue and reported that most stained mainly for collagen, some for keratin; the 2012 CDC-led study analyzed materials collected from skin surfaces and biopsies and reported that most were cellulose, likely cotton.
What it does not establish: Record measured size, magnification and relationship to skin. Color and shape alone cannot establish textile, hair, keratin or collagen identity. Results from one specimen stream do not settle another. Tiny filaments and a larger plug-like mass should be documented separately.
Material term · NLM MeSH
Keratin
A class of fibrous structural proteins. The National Library of Medicine describes keratins as the principal constituent of the epidermis, hair, nails and other horny tissues.
What it does not establish: An image cannot confirm keratin. Interpret staining or other material testing in relation to the particular sample and the question the method addresses.
Sources: [8]
Material term · NLM MeSH
Collagen
A protein that makes up about one third of total protein in mammals. The National Library of Medicine describes it as the main constituent of skin and connective tissue and the organic substance of bone and teeth.
What it does not establish: Recognizing collagen in a specimen does not by itself show its route to the surface or establish reactive perforating collagenosis.
Pathology concept · RPC literature
Transepidermal elimination
Passage of material from deeper tissue through the epidermis toward the surface. Faver and colleagues describe RPC as transepithelial elimination of altered collagen; their biopsy criterion is necrotic collagen eliminated into a cup-shaped epidermal depression.
What it does not establish: A collagen-positive object lying on the surface is not enough to demonstrate this route. Tissue architecture is part of the question.
Sources: [4]
Method concept
Specimen context / extraneous material
Where material was found and how it was collected: loose, resting on skin, adherent to a lesion, or demonstrated within a tissue section. Extraneous material can enter a sample during contact, collection or processing. Studies on both sides of the Morgellons debate report it: the 2012 CDC-led study found most birefringent material, generally compatible with cellulose, in superficial crust, at tissue edges or on biopsy surfaces without tissue reaction, although two biopsies with features suggesting prior ulceration or trauma showed foreign-body-type giant cells, one with cellulose and one with a silicon-containing material; the 2013 study excluded unattached filaments and noted plant material on one sample; the 2018 review reports pollen, arthropods and mostly textile “fuzzballs” in patient-supplied specimens.
What it does not establish: Consider both tissue-associated structures and contamination. Finding external material in one sample does not explain every lesion; reporting attachment in another does not establish one cause for all presentations.
How this reference was prepared
Terms were selected from the site’s fibers, histology and RPC articles. On October 13, 2026, each definition, attribution and citation was cross-checked against the cited sources: full text for references 1, 2, 3 and 7; abstracts and available excerpts for 4, 5 and 6; and the current NLM MeSH records for 8 and 9. This was an editorial citation check, not clinical review or scientific validation. This is a targeted editorial reference, not a systematic review or a new patient study.
Entry labels indicate where a word comes from and how it is used, not the quality of every claim in its source. The two Morgellons source papers come from the same research group; the 2018 review is included to trace its descriptors, and its authors’ observations are not counted as independent replication. Laboratory composition and clinical diagnosis remain separate questions. No prevalence estimates or treatment recommendations are inferred from these definitions.
References and source limits
International nomenclature consensus reached through Delphi voting by national dermatology societies. Definitions are paraphrased. It does not define “plug” or any Morgellons-specific lesion pattern.
Original examination of non-biopsy specimens (removed calluses with attached filaments, and one small tissue fragment) from four women. The authors state the study was too small for definitive conclusions about cause. Partly funded by the Charles E. Holman Foundation, on whose scientific advisory panel three authors served without compensation. Supports attributed specimen descriptions, not prevalence, a universal diagnostic pattern or a proven cause.
A review from the same group as reference 2, with specimen descriptions and figures. The comedo-like mass and follicular-cast passages appear under “Other MD findings,” which the authors base partly on their own unpublished examinations (2017); no methods or counts are given for those objects. Used to trace terminology, not as independent replication or controlled evidence. Full text read at the publisher’s site (Dove Medical Press).
Six-case report and literature review proposing three diagnostic criteria for acquired RPC: biopsy findings, clinical lesion form and adult onset. A central plug alone does not meet them. Only the published abstract was used here.
Retrospective trichoscopy study of 42 patients examined for suspected lice; 12 had pseudonits, including three with hair casts. Composition of the casts was not tested. It is not a study of Morgellons specimens. Checked against the abstract and available excerpts; the PMC full-text page could not be loaded directly.
Original biochemical study. The abstract reports keratin, partly degraded, in material from open acne comedones and describes comedones as containing a plug of cornified material. It does not establish the identity of a Morgellons-associated mass. Abstract used.
CDC-funded descriptive investigation in Kaiser Permanente Northern California with a broad self-reported case definition: 115 case-patients, 41 clinically evaluated, with skin-surface materials and biopsies analyzed separately. Some authors were Kaiser Permanente employees. Supports caution about collection context and composition. Its population and specimens differ from selected attached-tissue studies.
Official terminology for a protein class; not evidence that an unidentified object contains keratin.
Official terminology for a connective-tissue protein; not evidence for a particular filament’s composition.