Diffuse Alopecia Areata (DAA) is an uncommon variant of alopecia areata, a chronic and autoimmune condition that affects hair follicles, nails, and sometimes the retinal pigment epithelium. It is a common cause of nonscarring hair loss that causes round patches of baldness on the scalp or body. While classic alopecia areata causes well-demarcated, round, or oval bald patches, DAA presents with sudden, diffuse thinning of hair across the entire scalp, often without any visible patches. This makes it easily mistaken for other diffuse hair loss disorders, such as telogen effluvium or androgenetic alopecia. It is also known as alopecia areata incognita, a term first introduced by Rebora in 1987.¹ The exact mechanism that causes this form of diffuse hair loss remains unclear, but immune dysfunction disrupting the hair cycle is believed to be involved.

There are several clinical patterns of alopecia areata:

The patchy alopecia areata results in one or more reticular patches of hair loss.
Alopecia universalis causes near-total or total hair loss on all the hair surfaces of the body.
Alopecia totalis results in near-total or total hair loss on the scalp only.

Who gets the condition?

DAA is an uncommon event. It can affect both genders at any age. However, it is more predominant in females.²

To understand DAA, it’s helpful to first understand the normal hair follicle cycle, which includes:

Anagen (growth phase): Lasts 2 to 6 years. This is when the hair actively grows.
Catagen (transition phase): A short phase lasting 2 to 3 weeks, during which the hair follicle begins to shrink.
Telogen (resting phase): Lasts about 2 to 3 months. Hair is no longer growing and eventually sheds.

In DAA, many hair follicles prematurely shift from the anagen (growth) phase to the catagen and telogen phases, resulting in a higher proportion of resting hairs. This leads to sudden and widespread hair shedding, giving the appearance of diffuse hair thinning.

Causes of Diffuse Alopecia Areata

The causes of DAA include:

Genetic Predisposition:

DAA is not contagious and occurs more commonly in people with affected family members. It suggests that heredity may be a causative factor. Additionally, it shares genetic risk factors with some other autoimmune disorders. These disorders include celiac disease, type 1 diabetes, and rheumatoid arthritis.³

Autoimmune Mechanism:

This kind of alopecia is thought to be a systemic autoimmune disorder. The body attacks its own anagen hair follicles and stops or suppresses hair growth. The T lymphocytes cluster around the affected follicles and cause inflammation and hair loss. In a normal state, hair follicles are thought to be kept secure from the immune system (the phenomenon called immune privilege). A breach in the immune privilege state can be considered a cause of alopecia.⁴ DAA is associated with heightened inflammatory infiltration in affected scalp regions. The mononuclear cells and eosinophils contribute to the severity of the inflammation and hair loss.

Environmental & Lifestyle Factors:

Psychological stress and environmental factors might act as triggers to the condition. Lifestyle factors such as obesity and sleep quality can contribute to the onset and progression of the condition. Smokers have a high risk of developing alopecia areata due to the tobacco-induced Th17-mediated inflammation in the hair follicles.⁵

Some researchers suggested a link between sleep disorders and this condition, but the findings are still inconclusive.⁶ Obesity is associated with an increased risk of the condition. It is due to the adipokine dysregulation. This dysregulation promotes chronic low-grade inflammation and alters the immune response, as observed in other inflammatory skin conditions.⁷

Nutritional Deficiencies:

Nutritional deficiencies can also lead to DAA. The most commonly linked nutrients in the development of DAA are vitamin D and zinc. Biotin deficiency, whether due to poor diet or metabolic conditions like biotinidase deficiency, may contribute to hair thinning and diffuse hair loss.⁸

Symptoms of Diffuse Alopecia Areata

The symptoms of the DAA that differentiate it from the classic alopecia areata are:

Widespread thinning of hair across the scalp rather than discrete bald patches on the scalp.
Sudden reduction in hair volume and density.
Broken hairs
Newly grown short hairs
Easily removable hairs during gentle pulling
Scalp itching

The Signs observed under trichoscopy and trichogram are:

Telogen roots of hairs (hairs are in the resting phase rather than the growing phase).
Yellow dots (dilated hair follicles filled with keratin)
Black dots (remnants of broken hairs)
Exclamation hair marks (short, broken strands that appear thicker near the tip and thinner at the root)
Vellus hairs (light-colored, short hairs that are a sign of regrowth)
Dystrophic hairs (damaged or abnormal hair shaft)
Pigtail hairs (oval or circular-shaped hairs with tapered ends).⁹

Diagnosis of Diffuse Alopecia Areata

DAA is a clinical sign observed during examinations, while additional tests can also help diagnose the underlying cause of the conditions.

History & Physical Examination:

History can identify the genetic susceptibility and triggers of the condition. Females can accurately assess the percentage of hair loss based on the change in the circumference or diameter of their ponytail. The physical examination includes:

Scalp Examination:

The provider should determine the degree and pattern of hair loss. Assessment should involve the signs of scarring, scaling, redness, and inflammation. Other assessments include the shaft length, breakage, and diameter of the hairs. Further examination can be made through a dermatoscope or trichoscopy. Nail changes can also indicate the condition (nail pitting is associated with alopecia areata).

Macroscopic view of diffuse alopecia. — Macroscopic photo showing diffuse alopecia. The arrows indicate typical areas of alopecia. Image Courtesy: Post-SARS-CoV-2 Acute Telogen Effluvium: An Expected Complication by Monari rt al. 2022, https://doi.org/10.3390/jcm11051234, available via License CC BY 4.0.

Trichogram:

For a trichogram, the examiner plucks 20 to 50 hairs and examines them under a microscope to estimate the percentages of telogen and anagen hairs.

A normal trichogram result is <20 % telogen hairs and >80% anagen hairs.¹⁰
Telogen effluvium presents more than 25% telogen hairs.¹¹
The trichogram can also reveal exclamation mark hairs, characterized by hair shafts that taper toward the scalp, which are particularly suggestive of alopecia areata.

Blood Tests:

The blood tests that must be performed to identify the treatable causes include:

Thyroid function for assessing thyroid disease.
Complete blood count and ferritin for iron deficiency and anemia.
Liver function tests
Renal function tests
Antinuclear antibodies
Hormonal evaluation includes sex hormone-binding globulin, prolactin, and free androgen index in women with clinical signs of hyperandrogenism.

Hair Pull Test:

This test involves grasping 40 to 60 closely grouped hairs and applying gentle traction. The test result will be positive if more than 10% of the hairs can be pulled out easily. DAA, anagen effluvium and telogen effluvium present a positive hair pull test.

Scalp Biopsy:

Scalp biopsy is helpful in most cases if hair is lost. Indications for biopsy include lack of identifiable triggers, miniaturized hair shafts, chronic hair loss, and failure to exclude alopecia areata. Two four-millimeter punch biopsies should be taken from the vertex of the scalp at the site of clinical signs. Terminal and vellus hair counts and anagen-telogen hair ratio calculations should be done. In the case of acute telogen effluvium, a reversal of the normal anagen-to-telogen ratio can be observed. Characteristic peribulbar lymphocytic inflammation can be seen in alopecia areata. Low terminal to-vellus hair counts and miniaturization of the hair shafts are seen in cases of androgenetic alopecia.¹²

Treatment of Diffuse Alopecia Areata

DAA is a challenging condition to treat. The treatment increases hair growth, but the loss may recur when the treatment is stopped.

Minoxidil, topical corticosteroids, immunotherapy, and dithranol can induce short-term regrowth.
Systemic corticosteroids can also lead to regrowth, but the risk of long-term use of steroids can outweigh their benefits.
For adults with less scalp involvement, intralesional corticosteroid injections can temporarily speed up the regrowth of hair.
The new hair that grows back may not have the same color or texture as the was lost before.

The natural course of DAA is variable, and one-third of the patients recover spontaneously within six months. Almost 50 to 80% of the patients have persisting hair after a year. Some patients may have repeated episodes of DAA.¹³
The prognosis is worse for alopecia, which is severe at its onset.

Complications of Diffuse Alopecia Areata

Though hair loss has minimal harmful physical effects, it can be psychologically damaging. It can negatively impact an individual’s quality of life. The condition can be linked to several psychiatric disorders, such as anxiety and depression. Loss of hair from the scalp can often lead to scalp trauma (scalp hair provides an early warning of impending contact).

Diffuse Alopecia Areata Vs. Telogen Effluvium

DAA and telogen effluvium both cause diffuse hair loss but differ significantly in several ways. The key differences between the two are given in the table:

Features	DAA	Telogen Effluvium
Causes	DAA is an autoimmune disease targeting hair follicles, causing premature transition to the telogen phase.	Often triggered by physical or emotional stress, illness, surgery, childbirth, or nutritional deficiencies, causing a premature shift to telogen.
Onset of the Disease	Acute	Delayed
Symptoms	Broken hairs and exclamation hairs	Symptoms are not specific.
Histopathological Features	Perifollicular inflammation	Increased telogen follicles
Prognosis	Often favorable in mild and moderate conditions.	The prognosis is often self-limiting.
Treatment	Mainly corticosteroids. Other options include immunotherapy in extensive cases.	Mainly supportive care; minoxidil may be used to encourage regrowth in prolonged cases.

Final Remarks

DAA is a rare form of alopecia areata. A sudden and unexpected thinning of hair across the scalp characterizes it. Since diffuse hair thinning is a symptom of several hair loss conditions, it can be challenging to diagnose the DAA. See a dermatologist or doctor immediately if you notice increased hair shedding.

Refrences

1
Rebora, A., Alopecia areata incognita: a hypothesis. Dermatology, 1987. 174(5): p. 214-218.
2
Bergfeld, W., Diffuse hair loss: its triggers and management. Cleve Clin J Med, 2009. 76(6): p. 361-370.
3
Hordinsky, M. and A.L. Junqueira. Alopecia areata update. In Seminars in Cutaneous Medicine and Surgery. 2015.
4
Rajabi, F., et al., Alopecia areata: a review of disease pathogenesis. British Journal of Dermatology, 2018. 179(5): p. 1033-1048.
5
Dai, Y.-X., et al., Cigarette smoking, alcohol consumption, and risk of alopecia areata: a population-based cohort study in Taiwan. American Journal of Clinical Dermatology, 2020. 21: p. 901-911.
6
Sánchez-Pellicer, P., et al., How our microbiome influences the pathogenesis of alopecia areata. Genes, 2022. 13(10): p. 1860
7
Taylor, E.B., The complex role of adipokines in obesity, inflammation, and autoimmunity. Clinical Science, 2021. 135(6): p. 731-752.
8
Trüeb RM. Serum Biotin Levels in Women Complaining of Hair Loss. Int J Trichology. 2016 Apr-Jun;8(2):73-7. doi: 10.4103/0974-7753.188040. PMID: 27601860; PMCID: PMC4989391.
9
Alessandrini, A., et al., Alopecia areata incognita and diffuse alopecia areata: clinical, trichoscopic, histopathological, and therapeutic features of a 5-year study. Dermatology Practical & Conceptual, 2019. 9(4): p. 272
10
Wolff, H., T.W. Fischer, and U. Blume-Peytavi, The diagnosis and treatment of hair and scalp diseases. Deutsches Ärzteblatt International, 2016. 113(21): p. 377.
11
Malkud, S., Telogen effluvium: a review. Journal of clinical and diagnostic research: JCDR, 2015. 9(9): p. WE01.
12
Bergfeld, W., Diffuse hair loss: its triggers and management. Cleve Clin J Med, 2009. 76(6): p. 361-370.
13
Wolff, H., T.W. Fischer, and U. Blume-Peytavi, The diagnosis and treatment of hair and scalp diseases. Deutsches Ärzteblatt International, 2016. 113(21): p. 377.

Diffuse Alopecia Areata: Causes, Symptoms, and Treatment

In this Article [hide]