Pseudonits or Hair Casts – What is all About?
The term “pseudonits” refers to a series of structures of the hair shaft that may clinically mimic the nits of the head and pubic lice.
Hair casts or pseudonits are thin, elongated, cylindrical concretions that encircle the hair shaft and can be easily dislodged.1https://healthjade.net/pseudonits/ Hair casts or pseudonits are 2-7 mm long, discrete, firm, shiny, white, freely movable tubular accretions that encircle the hair shafts of the scalp.2https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250010/
Even though they are not unusual, there is scarce literature on them and underdiagnosis is common. They often occur in great numbers and must be correctly differentiated from pediculosis capitis.
Hair casts are indeed common in psoriasis, pityriasis amiantacea, fungal/bacterial infections, hair shaft abnormalities, pityriasis capitis, and seborrheic dermatitis. Pseudonits may be observed in various dermatological conditions. Their appearance may vary according to the pathogenesis.
How Common are Pseudonits or Hair Casts?
Despite the few cases reported in the literature, pseudonits or hair casts do not seem rare. Apparently, they are more common in females, particularly in patients who subject their hair to excessive traction for a long period. Pseudonits or hair casts seem to be most common among young adults.
Symptoms of Pseudonits
They can present as whitish scales, frequently seen in seborrheic dermatitis or psoriasis of the scalp, appearing at trichoscopy as easily detachable white, bizarrely shaped, amorphous structures on the hair shaft; although generally easily recognized at clinical examination, in children they can be misdiagnosed as nits.
Hair casts, also known as peripilar keratin casts, clinically appear as white, tubular, freely movable structures encircling the proximal hair shafts of the scalp, and that may be primary/idiopathic when there is no associated scalp condition, or secondary to traction alopecia (e.g., following tight hairstyles) or seborrheic dermatitis, psoriasis, lichen planopilaris, and pemphigus, unequivocally show their morphology at trichoscopy.
Sticky concretions surrounding the hair shaft of the axillary/pubic region may be observed in trichobacteriosis (also known as trichomycosis), an asymptomatic condition mostly caused by Corynebacterium spp. and generally associated with poor hygiene, obesity, and hyperhidrosis, at trichoscopy, typically resemble waxy and yellowish/whitish adherent aggregates forming a sheath surrounding the axillary hair shaft.
White piedra, a superficial mycosis common in tropical areas and caused by Trichosporon spp., is clinically characterized by the presence of multiple white-yellowish soft nodules along the hair shafts. At trichoscopy, the ovular scattered whitish masses are clearly shown.
Trichorrhexis nodosa is a congenital or acquired defect of the hair shaft characterized by dry, dull, and brittle hair with small grayish-white or yellowish nodules distributed irregularly along the shaft, which may result from repeated trauma, combing habits, and use of heat or hair weathering. At trichoscopy, it appears as localized whitish areas with fractured and frayed hair
Causes of Pseudonits
Pseudonits may be observed in various dermatological conditions. Their appearance may vary according to the pathogenesis.
Multiple etiological factors are implicated in pseudonits or hair casts causation. Pseudonits can be caused by several inflammatory scaling conditions such as psoriasis, seborrheic dermatitis, pityriasis amiantacea, dandruff, folliculitis decalvans, pemphigus vulgaris, or infective scalp conditions such as pediculosis capitis, trichorrhexis nodosa, white piedra, and trichomycosis.
Sometimes, hair shaft structural abnormalities such as trichorrhexis nodosa and monilethrix may also cause hair cast pseudonits. Residues of cosmetic hair sprays or deodorants and dry shampoos can cause pseudocasts that look very similar to nits.
Pseudonits hair casts are also seen in traction alopecia as a result of extraction of the root sheaths from excessive tension. Apparently, hair cast pseudonits are more frequently seen in females, who tightly plate their hair for prolonged periods.
This excessive traction by causing local scalp ischemia and inflammation promotes the development of pseudonits. In cases of pemphigus vulgaris of the scalp, acantholysis occurring in the outer root sheath epithelium can lead to the formation of pseudonits.
There are multiple case reports in the literature showing a causal association of hair cast pseudonits with lichen planopilaris, pseudopelade of Brocq, following psychological trauma, propionibacterium acne, and familial preponderance.
The Pathogenesis of Pseudonits
Pseudonits may be observed in various dermatological conditions. Their appearance may vary according to the pathogenesis.
The pathogenesis is often not clear, but their presence can be associated with pityriasis amiantacea, seborrheic dermatitis, hair nodes, scalp psoriasis, hairstyles with much traction, and also the use of hair sprays.3https://www.karger.com/Article/Fulltext/493741
All these conditions lead to the formation of more consistent root sheaths, which do not disintegrate during hair growth. However, they can occur without any previous abnormality.
The Diagnosis of Pseudonits
The diagnosis of pseudonits is generally clinical, but sometimes their presence may cause concern to both patients and physicians. Trichoscopy is a noninvasive and quick-to-perform tool that provides valuable information on a wide range of pediatric and adult hair and scalp conditions.
It has been reported to be useful for the diagnosis of head and pubic lice, being able to unequivocally identify the presence of parasites and nits, as well as to distinguish full nits from empty nits.
Electron microscopy studies showed that the true peripillous hair casts are usually compounds of the outer root sheath and are rarely composed of the internal root sheath, and often some are made up of both the sheaths, internal and external.
They can be easily slid along the hair shaft. This characteristic is of paramount importance in their diagnosis and helps in differentiating them from other scalp disorders, such as pediculosis capitis, piedra, trichomycosis, trichonodosis, and trichorrhexis nodosa.4https://www.cmaj.ca/content/185/9/E425
As is often the case, hair casts may initially be misdiagnosed as the nits of pediculosis capitis. Even though they are benign and have low-morbidity conditions, the fact that they are barely known leads to frequent diagnostic confusion, which may generate unnecessary costs and anxiety for both patients and physicians.
In most cases, trichoscopy allowed an easy differential diagnosis between nits and pseudonits by showing in detail their peculiar aspects. Hair examination using trichoscopy in routine clinical practice may provide useful information for making the correct diagnosis, ranging from common head and pubic lice infestations to rarer shaft abnormalities.
Differentiating pseudonits from nits is essential to make the correct diagnosis in order to prevent unnecessary treatment, anxiety, and/or embarrassment.
Treatment of Pseudonits
Treatment with keratolytic or coaltar shampoos is ineffective. The best result is obtained with a solution of 0.025% retinoic acid combined with manual removal of the cylinders with a comb, but the condition can recur after stopping the medication.
A review conducted by the authors found a notable decrease in the number of articles addressing hair casts in the last two decades and new generations of dermatologists have not incorporated it into their list of diagnoses for diseases of the scalp.
Watch the video below to know more about how to treat pseudonits:
A Life Experience of Pseudonits
From Canadian Medical Association Journal: “A 9-year-old girl was referred to our dermatology clinic for an assessment of whitish granules attached to her hair. She was otherwise healthy and had no history of pruritis of the scalp. Her parents had noticed the granules 8 months previously, and she had already received antiscabetic and antifungal treatments (3 weekly courses of 1.5% permetrin lotion, and daily ketoconazole shampoo for 2 mo).”
“On physical examination, we found easily sliding, whitish structures encircling the shafts of the patient’s hair. She did not have alopecia, and her scalp was not inflamed. A full inspection of the patient’s skin was normal. We diagnosed pseudonits and prescribed a keratolytic lotion of 3% salicylic acid. In addition, we recommended using a thin-tooth comb and avoiding traction movements when combing the hair. After a 2-month follow-up, the pseudonits had been resolved almost completely.”
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Frequently Asked Questions on Pseudonits
Treatment with keratolytic or coaltar shampoos is ineffective. The best result is obtained with a solution of 0.025% retinoic acid combined with manual removal of the cylinders with the comb, but the condition can recur after stopping the medication.
Apparently, hair casts are more common in young adults and females, particularly in patients that leave hair with excessive traction for a long period. Its etiology is unknown, but its presence can be associated with head pityriasis, seborrheic dermatitis, hair nodes, scalp psoriasis, and pityriasis amiantacea.
Nits (eggs) are tiny white specks attached to hairs close to the scalp. Unlike dandruff or sand, nits can't be shaken off the hair shafts. Best places to look for nits: behind the ears and along the hairline at the neck.
It's called “dandruff” (pityriasis capitis) when it's on a teenager's or adult's scalp, and “cradle cap” when it's on a baby's. Seborrheic dermatitis can occur in other areas of your body.
The female louse lays eggs (nits) that stick to hair shafts. Head lice are tiny insects that feed on blood from the human scalp. Head lice most often affect children. The insects usually spread through direct transfer from the hair of one person to the hair of another.
When you pull out your hair "by the root," you may observe a transparent swelling called the "bulb." The area above the bulb usually seen on plucked hair is the root sheath, the growing area of hair.
The name cowlick comes from the swirled effect left in the hair of baby cattle after being licked by their mothers. In humans, a cowlick is a small section of hair that grows at a different angle than the rest of the hair on your head.
Additional resources and citations
- 1https://healthjade.net/pseudonits/
- 2https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250010/
- 3https://www.karger.com/Article/Fulltext/493741
- 4https://www.cmaj.ca/content/185/9/E425
