Diagnosis of itchy skin

In the differential diagnosis of itching, it should be taken into account that mastocytosis, pemphigoid, or Duhring's dermatosis herpetiformis may initially manifest as itching on clinically healthy skin, and sebostasis in skin patients is hardly amenable to objectification.

In cases where it is impossible to associate itching with any dermatological disease, other causes should be sought. Generalized itching, in the absence of a primary skin disease, may be an important sign of an internal disease: uremic itching (kidney disease); cholestatic itching (mechanical jaundice, cholestatic hepatitis, primary biliary cirrhosis); endocrinopathic itching (diabetes mellitus, pruritus of pregnancy); paraneoplastic itching (Hodgkin's disease, visceral carcinoma); neurogenic itching (neurological diseases); psychogenic itching (mental illness); drug-induced itching (taking certain medications).

When examining the body of a patient complaining of itching, it is necessary to further differentiate between itching with and without skin manifestations. However, before concluding that there are no skin manifestations, it is necessary to conduct a most thorough examination of the patient's body, starting from the skin of the feet to the scalp, including the nasal cavity and external auditory canal, the anus, scrotum and vulva, as well as the nails and interdigital spaces. And only when all these areas of the body are unchanged, we speak of itching without skin manifestations. Next, it is necessary to pay attention to whether there is enlargement of the lymph nodes, spleen, exophthalmos or signs of diabetes mellitus and, of course, xerosis.

Correct assessment of itching is the most difficult task, requiring a thorough examination of the patient. A detailed anamnesis about the time of onset, course and intensity of itching is mandatory. It is always necessary to conduct a survey about the following characteristics of itching: generalized - localized; continuous - paroxysmal; progressive - fading; dependent on temperature, situation, time of day.

It is important to find out whether the itching is provoked or aggravated by factors such as water, heat, dryness or humidity, physical exertion, or cooling of the skin. It is always important to inquire about a stay in the tropics, contact with animals, medications, and dietary habits and favorite treats (dyes, additives, preservatives). A thorough anamnesis regarding atopy, as well as occupation, social status, and even sexual life, should also be included. Even without examining the patient's skin, a simple question about whether other family members or partners suffer from itching may already indicate an infectious genesis. Itching that subsides with falling asleep, does not disturb sleep, and increases markedly in intensity upon getting up indicates tension, which may be psychologically conditioned. Itching that prevents patients from sleeping or that causes them to wake up at night is more likely to be caused by a systemic disease. Various skin diseases are characterized by continuous itching, such as atopic dermatitis, in which only sleep due to exhaustion "covers up" the attacks of itching. Night sweats and subfebrile temperatures associated with itching are almost pathognomonic for Hodgkin's disease and are often provoked by evening alcohol consumption. These few examples focus the doctor's attention on the correct formulation of questions when collecting anamnesis from a patient with itching, especially without typical skin manifestations.

History of the disease with skin itching

• Onset (sharp, gradual)
• Current (continuous, intermittent)
• Character (piercing, burning)
• Duration (days, months)
• Time (cyclical, during the day, at night)
• Degree of suffering (impact on daily life)
• Localization (generalized, limited)
• Provoking factors (water, temperature, friction)
• Taking medications
• Environmental factors (occupation, hygiene, pets)
• Psychotraumatic situations in the recent past
• Allergies, atopy
• Travel history (business trips, vacations)
• Sexual history
• Previous therapy

Itching is rarely continuous. Sometimes it depends on a change in temperature, for example, when entering a warm room after being in the cold air. Itching may occur in crises during the day, but most often it intensifies at night. In some dermatoses (for example, simple subacute prurigo), a limited inflammation of the skin is scratched until blood flows, only then does the itching stop. Often with eczema, itching intensifies with scratching and subsides when the patient is exhausted from scratching. Itching is known to be absent during the day and revived at night: a typical anamnesis for scabies.

Determining itching of unknown genesis is a major problem of differential diagnosis. It is at a later age that one should think about the simultaneous presence of several diseases that can cause itching (age-related sebostasis in combination with hormonal disorders, nutritional deficiency or malignant tumors). In practice, it is advisable to conduct a trial local treatment with indifferent ointments on a fat basis. Sometimes it is difficult to differentiate secondary effects of itching on the skin from primary dermatoses. The effect of prolonged itching on the patient's psyche, causing prolonged insomnia or neurasthenia, should not lead to an erroneous diagnosis of a psychiatric disease. It is important to establish whether the patient has lymphadenopathy or hepatosplenomegaly, since lymphomas can be accompanied by itching. Itching without skin rashes sometimes serves as an indicator of HIV infection, often accompanied by oral candidiasis and lymphadenopathy. Sometimes, when examining the skin, rashes are mistakenly considered to be the cause of itching, although in fact they are its result.

The following aids may help in making a diagnosis of itchy skin: a magnifying glass (possibly a microscope), a glass ruler, a pair of small tweezers, a blunt-ended instrument (spatula), a probe, small anatomical tweezers. In addition to a visual examination, the physician will need the patient's sense of touch (palpation, general examination), and in some cases, his fingernail. Prior to the clinical examination, the patient's medical history should be taken as thoroughly as possible. For the examination itself, the patient is asked to undress completely. In cases of itchy conditions, it is important to examine every inch of the patient's skin, even if the patient denies having any visible skin lesions.

In addition to the history and physical examination, a targeted individualized evaluation program should be performed, as pruritus may precede the manifestation of systemic disease. Patients should be closely monitored thereafter.

The minimum laboratory program for determining possible causes of itching in the absence of typical manifestations of any dermatosis should include, in addition to determining the parameters of inflammation (ESR and C-reactive protein), a differential blood test with counting the number of eosinophils and platelets, transaminases with alkaline phosphatase and bilirubin, as well as transferrin and iron, urea and creatinine, uric acid and sugar, calcium and phosphate. The program is completed by studying hormones, thyroid and parathyroid glands, determining the total level of IgE in connection with evidence of intestinal parasitosis.

Examination plan for a patient with itchy skin

• General examination (temperature, sweating, fatigue, weight loss)
• Skin (pigmentation, dryness, icterus, traces of excoriations)
• Nails (discoloration, dystrophy, onycholysis)
• Eyes (exophthalmos, change in scleral color)
• Endocrine system (tremor, thermoregulation disorder, polydipsia, polyuria)
• Blood system (anemia, bleeding, lymphadenopathy)
• Gastrointestinal (nausea, vomiting, stool, drip and color incontinence)
• Urogenital system (urine color, urinary incontinence, menstruation, pregnancy)
• Nervous system (headaches, paresthesia, visual disturbances)
• Mental status (mood, sleep disturbances, hallucinations, delirium)

Examination plan for a patient with skin itching

• Complete blood count
• Blood biochemistry (alkaline phosphatase, bilirubin, urea, creatinine)
• T4 (thyroxine), TSH (thyroxine-binding globulin)
• Blood test for iron, ferritin
• Blood test for total protein and protein fractions (a1, a2, beta, gamma)
• HIV serology (HIV ELISA)
• Fecal occult blood test
• Analysis of feces for helminth eggs
• Urine analysis (5-hydroxyindoleacetic acid, 17-ketosteroids)
• Skin biopsy (histology, immunofluorescence, electron microscopy)
• X-ray and ultrasound examination
• Endoscopy (fibroesophagogastroduodenoscopy, rectoscopy, colonoscopy, laparoscopy)

If pruritus associated with paraneoplasia is suspected, appropriate investigations using tumor markers and minimally invasive studies such as chest x-ray and ultrasound should be performed.

Sometimes it is helpful to determine the level of histamine, serotonin and tryptase (diffuse mastocytosis, nephropathy, hepatopathy). In case of lichenoid lesions, biopsy will allow to exclude granulomatous dermatoses. Studies associated with infections should always be carried out purposefully.

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