Prurigo nodularis Definition
It is a chronic inflammatory disorder characterized by itchy eruptions of pale, dome-shaped papules. It is a bothersome condition that interrupts the day-to-day routine of the patients as a result of constant scratching. For simplicity, it is abbreviated as PN. The condition is also known by other names like:
- Hyde’s disease
- Nodular prurigo
- Lichen corneus obtusus
- Picker’s nodules
- Nodular neurodermatitis circumscripta
- Nodular lichen simplex chronicus
Prurigo nodularis Symptoms
Frequent episodes of itching can lead to development of distinct, excoriated, nodular, hyperpigmented/purpuric lesions. They may measure more than 0.5 cm in width and depth. The cutaneous eruptions are either flat, umbilicated, or covered with crusted or scaly surfaces. These pruritic nodules are usually seen on the arms and legs, but may appear on the other parts of the body such as the trunk, face, scalp and feet. The hair follicles may sometimes give rise to such nodules and could well develop before the beginning of an itch/scratch cycle. The nodular lesions are normally symmetrical in distribution and may have a tendency to multiply. The pruritic episode may last for a long time to cause scaling and thickening of the skin.
Prurigo nodularis Causes
The exact cause of PN is unknown. It is also difficult to determine the relation between the appearance of the lumps and itching. Although some psychological/psychiatric illnesses may induce the problem, most cases of nodular prurigo are associated with the following conditions:
- Linear IgA disease
- Renal failure
- Hepatic disorder
- Thyroid problem
- Polycythaemia rubra vera
- Brachioradial pruritis
- Hodgkins disease
- Gluten enteropathy
- Strongyloides stercoralis
- Atopic dermatitis
- Hay fever
- Hepatitis C
- Helicobacter pylori infection
- Skin cancer
- Insect bite
Prurigo nodularis Histology/Histopathology
In case of PN, the pathological reaction pattern is marked by bulbous thickening of squamous epithelium with a sudden transition between lesion and adjacent epidermis. The nodular lesions, when observed under a microscope, have a vitreous cytoplasm. A prominent acanthosis, hypergranulosis, and superficial dermal fibrosis are the other histological features of the condition.
Prurigo nodularis Pathophysiology
Lichenification and hyperpigmentation of the skin are some of the permanent effects of repetitive scratching, picking, or rubbing of the nodular lesions. These papules are highly obstinate as they normally show no signs of healing. A history of chronic severe pruritus as well as secondary skin infections can be linked to Hyde’s disease. The acute inflammatory response within the skin is induced when the activity and the number of calcitonin gene-related peptides and substance P immunoreactive nerves are abruptly increased. However, the etiology of the condition is yet to be determined by medical experts.
Prurigo nodularis Diagnosis
Physical examination of the skin is essential for assessing the nature of the nodules. The cutaneous signs of the condition may help in revealing the cause of pruritic sensations. An elevated amount of eosinophils is evident from the biopsies of papular lesions. A series of blood tests could assist healthcare givers to identify the underlying hepatic, renal, or metabolic disorders by detecting the following components:
- C-reactive protein
- Alanine transaminase
A patch test could be conducted to identify whether a specific substance causes allergic inflammation of skin along with the development of nodules.
Prurigo nodularis Differential Diagnosis
The dermatologic symptoms are associated with a number of other skin disorders that needs to be distinguished by physicians during diagnosis. Some of these include:
- Pretibial myxoedema
- Squamous cell carcinoma
- Lymphocytoma cutis
- Lymphomatoid papulosis
- Cutaneous horn
- Molluscum contagiosum
- Multicentric reticulohistiocytosis
- Atypical fibroxanthoma
- Hyperkeratosis lenticularis perstans
Prurigo nodularis Treatment
There is no standard therapy for PN as it shows resistance to a wide spectrum of antibiotics. However, the following treatment methods could be used for ameliorating the symptoms:
These medications usually work by decreasing inflammation and reducing the episodes of itching. Topical administration of steroids may soften and smooth the pruritic nodules. The outcome is better when the anti-inflammatory drugs are given to the patients, orally or intralesionally.
These are moisturizers that can be used to cool and soothe the affected skin.
Pulsed dye laser
The papular lesions can be destroyed and eliminated with the aid of pulsed and tunable lasers.
The technique involves the use of liquid nitrogen or probe in order to freeze the nodules and destruct them.
This topical skin preparation induces a burning sensation in the skin for stopping the itch.
The synthetic vitamin D ointment aims to clear the papular growths on the skin.
Coal tar ointment
It is a keratolytic that relieves itching and irritation caused by the nodular lesions.
Additionally, doctors may prescribe the following medications for treating the systemic conditions:
- Anesthetic creams
- Immunomodulatory macrolide
- Psoralen combined with ultraviolet A
If the cause of the condition is related to psychological depression then habit reversal therapy, cognitive behavioral therapy, and administration of anxiolytic drugs are some of the curative options for the sufferers.
Prurigo nodularis Complications
Although PN is a benign and non-contagious disorder, some patients may develop functional impairment and morbidity due to constant scratching. In few cases, the lesions may cause permanent pigmentation and scarring.
Prurigo nodularis Prognosis
The pruritic nodules are not self-limiting and may take long time to resolve despite early treatment. The outlook of the condition can improve spontaneously if healthcare professionals are able to break the itch/scratch cycle. A proper diet and use of home/natural remedies can prove to more effective than drug therapy.
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