Leukoplakia is the appearance of patches of lighter than normal skin color at the skin and mucous membranes, mainly due to skin hypopigmentation or depigmentation of pigment. Leukoplakia can be congenital or acquired. It can also be a skin manifestation of other diseases. Are white patches always vitiligo? What other skin diseases are included?
1. Acquired leukoplakia
1.1 Vitiligo.
According to the morphology, location, distribution range and treatment response of the white spots, there are two types, i.e., common type (limited, scattered, pancytopenia, extremity type) and segmental type, and two stages, i.e., progressive and stable stage. Pathologically, vitiligo mainly affects melanocytes in the epidermis, and melanocytes in the hair bulb are also involved to some extent, manifesting as reduction or disappearance of melanocytes and melanin granules in the epidermis and mucosa.
The diagnostic criteria for vitiligo are: ① usually onset in childhood or adolescence, manifested as depigmented white spots of different sizes and shapes, surrounded by normal color or increased pigmentation; ② the lesions are commonly found on the face, neck, back of the hands and trunk, mucous membranes and surrounding skin are also susceptible.
The lesions are usually found on the face, neck, back of hands and trunk, and also on the mucous membranes and surrounding skin, such as the eyes, nose, mouth, ears, nipples, umbilicus, penis, female genitalia and anus; they are also commonly found on traumatic sites, and the hair on the white spots usually turns white.
1.2 Halo nevus.
Also known as eccentric acquired leukoplakia, it is characterized by a circle of hypomelanotic white halo around nevus melanocytic nevus. It may be related to the destruction of epidermal melanocytes in the halo due to humoral and cytokine factors. Histopathology shows that the central nevus is mostly a cellular nevus, and the white halo around the nevus shows vitiligo-like changes.
1.3 White furfuraceous rash.
That is, simple furfuraceous rash, mostly for children’s facial superficial dry scaly white spots, the edge is not clear, the surface is dry, with the eyebrows, cheeks and chin more common. dp microscopic performance for the edge of the lesion is not obvious light white or light red spot, the surface is covered with a small amount of fine grayish white furfuraceous scales.
1.4 Idiopathic punctate hypopigmentation.
This disease is distinguished from vitiligo, lichen planus and secondary leukoplakia by the white spots with clear edges that do not continue to expand. It is thought that this disease and senile leukoplakia are the same disease, and studies have shown that senile leukoplakia increases significantly after entering the age of 60, probably due to a significant decrease in the number of dopa-positive melanocytes in the skin as we age. The leukoplakia dermoscopically appears as pale white or pure white round or oval slightly depressed lesions, which occur on the chest, back and extremities of middle-aged and elderly people.
1.5 Mucocutaneous leukoplakia
(vulvar leukoplakia, male genital mucous membrane leukoplakia, anal mucous membrane leukoplakia): vulvar leukoplakia is vulvar dystrophy, a chronic disease of female vulvar skin mucous membrane degeneration and melanin change, with vulvar itching and melanin loss as the main clinical features, often accompanied by rash. It is associated with local factors such as local irritation, neurovascular dystrophy, metabolic disorders and other factors such as infection, autoimmunity, sex hormones, genetics, oxidation and antioxidation. The white spots have normal number of melanocytes, rough surface, hyperkeratosis, and toughness to touch can be distinguished from vitiligo of the pubic area. The male genital white spots are mostly seen in the inner foreskin, coronal sulcus, glans area, with unclear border and irregular shape white spots. Anal mucosal leukoplakia is often accompanied by itching.
1.6 Sclerosing atrophy.
Sclerosing atrophic moss is a chronic inflammatory skin disease. It is common in middle-aged and elderly women, and this disease often occurs inside and outside the labia majora and around the anus, and only 20% of patients have skin lesions outside the pubic area, mostly on the upper trunk and upper arms. The lesions on the pubic area are often well-defined white patches surrounded by edematous erythema, with hard, shiny skin and intense itching. The lesions outside the pubic area are mostly asymmetric pink, ivory-white, fused patches or patches with clear borders. Parchment-like atrophy appears on the patches in later stages. The pathological changes of this disease are specific, showing lymphocytic infiltration, follicular keratosis, spiny layer atrophy, basal cell liquefaction degeneration, and purifying changes in the superficial dermis.
2.White spots caused by congenital, genetic and developmental factors
2.1 Non-pigmented nevus (nevusdepigmententosus, ND).
That is, depigmented nevus, which is a rare, stable, limited, congenital hypomelanotic disease, divided into isolated, segmental and systemic types. The clinical diagnosis has been based on the diagnostic criteria proposed by Coupet: (1) the white spots occur at birth or shortly after birth; (2) the distribution of white spots remains unchanged throughout life; (3) there are no histological changes or sensory changes at the lesion site; and (4) there is no melanin deposition at the edge of the white spots.
Under the Wood lamp, the white spots are yellowish-white without fluorescence, and under the DP, the borders are indistinct, without pigment deepening, with individual jaggedness, and sometimes white hairs are visible.
2.2 Anemic nevus.
It is a congenital limited vascular development defect. The blood vessels in the affected area have normal structure but abnormal function and are in a contracted state due to enhanced sensitivity to catecholamines, resulting in pale white skin, which is usually distributed unilaterally or limited to a certain area. The anemic nevus cannot cause congestion reaction after rubbing, will local congestion and redness of lesions occur after patting. At the same time, because the skin melanin in the lesion area of anemic nevus is normal, the normal skin around the lesion is the same color as the lesion after blood loss by slide pressure, thus the lesion disappears.
The dermoscope shows single or multiple pale spots of different sizes, round, oval or irregular linear, with irregular but clear borders, and there may be clusters of small macules].
2.3 Pemphigoid.
A rare autosomal dominant disorder. It is characterized clinically by triangular or diamond-shaped white spots in the frontal midline, often combined with white hair, called white frontal hair, and symmetrically distributed melanin-deprived white spots in the mid thorax and abdomen and extremities, interspersed with melanin patches, with stable lesions and non-pigmented borders.
2.4 Progressive symmetrical pigmentation abnormalities.
That is, idiopathic punctate melanopenia, an autosomal dominant disorder. It is characterized clinically by patchy symmetrical leukoplakia on the extremities, especially on the dorsum of the hands and feet. The common pathology sees an increase in the number of melanocytes at the basal cells of the melanosis site and a decrease in the number of melanocytes at the hypomelanosis site.
2.5 Anaplastic pigmentary incontinence.
That is, Itochromatosis pigmentosa, an autosomal dominant, congenital neurodermatosis with white spots present at birth, often associated with impaired intellectual development and epilepsy. The disease is distinguished from vitiligo and albinism by unilateral (occasionally bilateral) leukoplakia of bizarre morphology, without conscious symptoms or with other systemic diseases and with onset shortly after birth, without choroidal melanin loss. The pathological manifestations are reduced melanin granules in the basal cell layer and partial complete absence.
2.6 Albinism.
It is a group of genetic diseases related to melanin biosynthesis and can be divided into ocular- cutaneous albinism, ocular albinism, Hermansky-pudlak syndrome, Chediak-Higashi syndrome, Usher and Griscelli syndromes. It is mainly due to a deficiency or insufficiency of tyrosinase enzymes, which do not convert the intermediate product of protein metabolism “dopa” into melanin. The disease is characterized by widespread skin lesions, white or yellowish hair, and photophobia due to lack of melanin in the eyes.
2.7 Phenylketonuria.
Autosomal recessive metabolic disease, due to phenylalanine hydroxylase defects resulting in impaired phenylalanine metabolism. Very rarely, it is caused by a deficiency of tetrahydrobiopterin. After 3 months of age, the child may have delayed intellectual development, light hair and skin color, and a ratty urine odor in urine and sweat, with abnormal mental behavior. The diagnosis can be confirmed by combining the urinary phenylketonate level.
3.White spots caused by pathogens
3.1 Lichen planus.
Commonly known as sweat spot, a chronic fungal disease of the superficial keratin layer of the skin caused by Malassezia furfur. In adults, hypomelanotic patches or yellow-brown patches with furfur-like scales appear on the chest, back, axillae, and upper arms, leaving white patches after fading. In children, white patches with clear edges are covered with very fine scales, mostly on the forehead and cheeks.
3.2 Nodule-like leprosy.
Typical lesions are red patches with clear edges, sometimes elevated, rough and dry surface, covered with scales, and loss of animal hair. Skin hyperalgesia white spots is one of the important symptoms of the disease, white spots with clear edges, the surface can appear thin scales, white spots with little or no sweating. Pathological manifestations are tuberculosis-like infiltration, with Langerhans giant cells in the late stage, but no caseous necrosis is formed.
3.3 Syphilitic leukoplakia, pseudosyphilitic leukoplakia.
Stage II syphilis is mostly manifested by roseola, follicular rash, papular scales, pustular rash, perianal and external genital flat warts, oral mucosal damage, but it can also appear with polymorphous erythema and skin leukoplakia as the first symptoms
However, patients with erythema multiforme and leukoplakia as the first symptom may also appear, mainly on the chin and neck area, often together with the rash of syphilis. Syphilis white spots may appear similar to “vitiligo”-like changes, the white spots may increase in size and fuse with each other, but the edges are not clear and the shape is irregular. Positive syphilis seropositivity.
Pseudosyphilitic leukoplakia, the lesions are pale white patches, round or oval, with unclear boundaries, smooth surface, no inflammation, and can fuse with each other. Unlike syphilitic leukoplakia, the waist, back, abdomen, chest and arms are its preferred sites. The pathological manifestations are regional melanocyte reduction under the epidermis and mild vacuolar degeneration of some epidermal cells.
4.Secondary leukoplakia
4.1 Post-inflammatory hypopigmentation.
Many inflammatory skin diseases, such as white Wickham striae of lichen planus, lupus erythematosus, psoriasis, pityriasis rosea, eczema, neurodermatitis, post-burn scar, herpes zoster and drug rash, etc. After inflammation, secondary hypopigmentation occurs, which is mostly temporary and does not require treatment and can recover by itself.
4.2 Occupational leukoplakia.
Recent studies suggest that phenol, catechol and its derivatives hydroquinone, p-tert-butylcatechol, p-tert-butylphenol and p-tert-pentylphenol act destructively on melanocytes through direct contact with the epidermis of the site, or partly through respiratory and digestive tract intake, producing white spots.
4.3 Hypomelanosis secondary to endocrinopathies.
Hypopituitarism due to lack of melanocyte stimulating hormone in endocrine diseases can produce leukoplakia.
5. Syndromes with leukoplakia as a manifestation
5.1 Marshll-White syndrome
(Bier’s anemia), vascular pitting: the lesions are pale white spots surrounded by diffuse red spots or cyanosis, mostly occurring at the ends of the limbs, palms and dorsum of the feet, if the affected limbs droop for a period of time, the white spots are more prominent, and the white spots can disappear when the affected limbs are raised, not affected by temperature, and there is no obvious difference between winter and summer, while vascular pitting of the skin is obvious in low temperature. Vascular punctate discoloration shows a marble-like appearance with intermingled erythema and white spots at the end of the extremities, which is more common in women.
5.2 Tietz syndrome.
Tietz’s syndrome is characterized by the appearance of white patches of skin similar to albinism at birth, complete deafness, and dysplastic eyebrows. Recent studies suggest an association with mutations in transcription factors associated with microphthalmia.
5.3 Ziprkowski-Margolis syndrome.
Congenital deafness, heterochromatic iris, X invisible inheritance, hypermelanotic rash on congenitally melanin reduced skin, white hair and hair on pigmented patches.
5.4 Alezzandrini syndrome.
Visual impairment due to retinal degeneration on one side, vitiligo and whitening of eyebrows and eyelashes on the same side months or years later, and hearing abnormalities in some patients.
5.5 Waardenburg syndrome.
Autosomal dominant disorder. There are congenital anomalies such as frontal white hair, unilateral or bilateral congenital deafness, heterochromia of the iris, widened pupillary distance, limited eye movement or nystagmus, and widening of the nasal root.
5.6 Vogt-koyanagi syndrome.
Uveitis is bilateral and may present with alopecia, hair whitening, symmetrical vitiligo, and other symptoms.