The main clinical features of this disorder are scaling, increased wrinkling of the palms and soles, and follicular hyperkeratosis. Scaling is most pronounced on the extensor surfaces of the limbs, with less involvement of the skin on the back, abdomen, and scalp. The scales are predominantly small, thin, with wavy edges, and range in color from white to dark gray to brown. The shins have the darkest and thickest scales, which are polygonal in shape and tightly packed. Follicular hyperkeratosis, in the form of small dry nodules at the hair follicle openings, is observed on the thighs, shoulders, forearms, and buttocks, and may also be localized on the trunk and face. Palpation of the affected areas reveals a "grating" sensation. The palms and soles have an accentuated pattern, increased wrinkling, giving them an aged appearance. Painful cracks often appear on the soles during the summer.

Nail plates are brittle and often break from the free edge, sometimes leading to onychohysis. Hair becomes thin and sparse.

Expression of ichthyosis vulgaris is variable. Abortive forms of the disease occur, characterized by dry skin with mild scaling and increased wrinkling of the palms and soles.

The disease is characterized by the following signs:

• Presence of ichthyosis in the patient's first and second degree relatives.
• Clinical symptoms appearing within the first year of life (3-7 months) or later (up to 5 years).
• Clear seasonality with improvement in summer and worsening of clinical manifestations in winter.
• Association with allergic diseases: Individuals with vulgar ichthyosis are prone to allergies and atopy. The frequency of co-occurrence with atopic dermatitis reaches 40-50%. Concurrent manifestations of bronchial asthma, vasomotor rhinitis and urticaria are common. Food and drug intolerance is typical.
• Associations with gastrointestinal diseases (gastritis, enterocolitis, biliary dyskinesia) are seen, with cryptorchidism or hypogenitalism observed in a minority (3% of patients). Patients are susceptible to bacterial, viral and fungal infections.

Dryness of the skin is observed immediately after birth or in the first weeks of life. Later, light and dark brown scales appear on the extensor surfaces of the limbs. The nape of the neck has a "dirty" appearance due to the accumulation of scales. The armpits, elbow creases, and genitalia are unaffected. A distinguishing feature from other forms of ichthyosis is the absence of skin involvement on the face and hands, resembling "gloves".

The disease is characterized by the following signs:

• Presence of ichthyosis in 1st and 2nd degree relatives of the patient. Only males are affected. Females are heterozygous carriers of the defective gene without clinical manifestations of the disease.
• Clinical symptoms appear at birth or in the first weeks of life.
• Slight seasonality, with most patients noticing an improvement in skin condition during the summer.
• Absence of associations with atopic dermatitis and respiratory atopy in most patients.
• Corneal opacity without visual impairment (in 50% of patients), cryptorchidism (in 20% of patients)

Characterized by generalized lamellar scaling, always accompanied by palmoplantar hyperkeratosis, a constant clinical sign of the disease. Scales on smooth skin are usually small and light, while on the shins they are larger and form lamellar scales. Some patients may have deformity of the auricles.

The disease is characterized by the following signs:

• Presence of ichthyosis in the patient's 1st and 2nd degree relatives.
• Clinical symptoms appear from birth: the infant is born with a collodion membrane or in a state of generalized erythroderma, followed by the development of generalized lamellar scale about 6-7 months after birth.
• Absence of physical and mental developmental disorders in patients.
• Absence of seasonality.

Hyperkeratosis with large keratinized plates is observed in the areas of large natural skin folds (knees, elbows, wrists, ankles, neck folds, and axillae). The hyperkeratotic patches are brown, brown-black, or dirty gray in color. On the background of hyperkeratosis, vesicles with serosanguineous contents initially appear, followed by secondary infection. At the same time, there is an increase in body temperature and enlargement of regional lymph nodes. When the keratinized layers are sloughed off, eroded areas with prominent papillary growths remain. Unpleasant odor is common due to frequent secondary infections.

The disease is characterized by the following signs:

• Presence of ichthyosis in the patient's 1st and 2nd degree relatives.
• Clinical symptoms appear from birth: the infant's skin appears macerated at birth, soon after birth it becomes dry, and in the large natural folds it becomes thickened and coarsely folded.
• Seasonal exacerbation of the disease: the appearance of blisters and subsequent infection usually occurs in the fall and spring.

The condition affects the entire skin, forming a continuous, variable-thickness stratum corneum of whitish-yellow or grayish-brown color that cracks and forms deep furrows on the joint surfaces. The head of the patient has a thick layer of horny deposits with short, sparse or absent hair. The mouth is wide open due to pronounced infiltration of the soft tissues, with deep fissures at the corners. The lips are thickened, the mucous membranes are turned outwards, there is a pronounced ectropion and sparse eyelashes. The ears are deformed and pressed tightly against the skull or turned forward. The nostrils and auditory canals are lined with keratinous, plug-like deposits.

The disease is characterized by the appearance of clinical symptoms from birth: at birth, the baby's skin resembles a rough, dry horny shell of grayish white or purple color that darkens within the first few hours after birth. In 80% of cases, newborns are premature.