What Is Nevus Comedonicus?
Nevus comedonicus (NC), also called comedo naevus, is a rare disorder that affects the skin. Kofmann initially suggested naming the condition comedo nevus in 1895. It is believed to be an epidermal nevus affecting hair follicles or brought on by hamartomatous pilosebaceous tissue proliferation. This rare developmental anomaly is clinically presented as increased follicular openings that are grouped together and frequently arranged linearly. Open comedones form when dark keratin plugs finally fill in the follicular holes. These lesions naturally result in significant scars development as a post-inflammatory response.
The syndrome can manifest at any point between birth and middle life; however, it typically first manifests at birth (in fifty percent of cases) or before the age of ten. These lesions typically occur in the face, neck, upper arms, chest, and belly. The palm, glans, penis, ear, scalp, and breast tissue are among the uncommon locations that may be affected. Although they only show up on the skin, they could be an aspect of a nevus comedonicus syndrome that includes skeletal, neurological, ophthalmic, and other cutaneous disorders.
What Causes Nevus Comedonicus?
Nevus comedonicus causes are still mostly unknown. It is believed that somatic mutations (any alteration at the cellular level in the cell that is not an egg or sperm cell occurring after conception) during embryonic development cause nevus comedonicus. FGFR2 (fibroblast growth factor receptor 2) mutations are significant because they result in increased IL-1 (interleukin-1) alpha expression. Somatic mutations in the NEK9 (NIMA-related kinase 9) gene have been reported recently as the cause of nevus comedonicus.
This results in the disruption of normal follicular differentiation and the activation of NEK9 kinase. Even though these DNA alterations have been detected in both follicular and non-follicular tissue, NEK9's role in the pathophysiology of nevus comedonicus has been suggested to be follicle-specific. Various other diseases have been linked with this gene mutation, including Apert’s syndrome, craniosynostosis syndrome, and chondrodysplasia syndrome.
What Are Nevus Comedonicus Symptoms?
Comedone naevi usually manifests as a solitary cluster of dark, hyperkeratotic papules and horny plugs. Generally forming a linear, zosteriform, or blaschkoid pattern, these lesions are arranged in accordance with Blaschko's lines, which represent embryonic cell movement paths. They can affect anywhere from a few millimeters to half of the whole body, and they are typically unilateral.
Nevus comedonicus usually affects the upper extremities, neck, face, and trunk. Rarely seen sites include the scalp, penis, palms, and soles. Verrucous nodules may be visible when they affect the elbows and knees.
Lesions resembling hidradenitis suppurativa (a condition leading to small, painful lumps under the skin) may result from mechanical stress in the intertriginous zones. Although the lesions are typically asymptomatic, they may become inflammatory or infected and cause consequences such as cysts, abscesses, or recurrent bacterial infections. Lesions can change in appearance over time; some may become more noticeable or grow into larger nodules or plaques.
What Are the Associated Signs and Symptoms of Nevus Comedonicus?
In some individuals, nevus comedonicus is associated with various systemic abnormalities, a condition known as nevus comedonicus syndrome. The mechanisms that explain these associations are still being determined. Anomalies of the skeletal, ocular, neurological, and other organ systems may be present in this illness.
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Skeletal Abnormalities - Nevus comedonicus syndrome patients may have multiple skeletal deformations, including limb asymmetry, scoliosis (sideways curvature of the spine), or other bone abnormalities. Orthopedic intervention may be necessary for these anomalies, ranging from minor to severe.
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Neurologic Manifestations - Seizures, delayed development, epilepsy, transverse myelitis, microcephaly, electroencephalogram abnormalities, and other anomalies of the central nervous system are examples of neurologic involvement in nevus comedonicus syndrome. Treating these manifestations requires a multidisciplinary approach involving dermatologists, neurologists, and other specialists.
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Eye Disorders - Nevus comedonicus syndrome patients may also have ocular anomalies, such as colobomas (an area of missing tissue in the eye) or other congenital eye disorders. Frequent ophthalmologic examinations are necessary for the early diagnosis and treatment of these problems.
How Is Nevus Comedonicus Diagnosed?
Nevus comedonicus is mostly diagnosed clinically based on the unique appearance of the lesions. Dermoscopy and a comprehensive skin examination are useful in differentiating nevus comedonicus from other disorders that appear similarly.
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Skin biopsy is not usually necessary in all cases. It will reveal epidermal invasions with mild atrophy that resemble larger hair follicles. The invasions feature common lobes of sebaceous glands, concentric laminae from keratin synthesis, and acanthosis.
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Dermoscopy has recently been used to help diagnose nevus comedonicus. Dermoscopy reveals the characteristic lesions of the comedones. Many pale and dark brown, round or barrel-shaped homogeneous regions with noticeable keratin plugs are typical dermoscopy results reported.
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Genetic testing is not regularly done. However, it can help diagnose nevus comedonicus syndrome from other hereditary diseases or in cases where it is suspected. Identifying particular mutations may provide knowledge of the underlying pathophysiology and help in treatment.
How Is Nevus Comedonicus Treatment Performed?
Localized nevus comedonicus usually does not require medical attention until it causes consequences like an infection. There are no documented cases of spontaneous regression. It is important to provide nevus comedonicus treatment as needed.
Tropical Treatment:
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Topical retinoid cream (Tretinoin 0.1%) is effective in removing nevus comedonicus. It acts by fastening the process of epithelial exfoliation. This chemical causes keratin plugs to be expelled from comedonal lesions. It can be used along with Mometasone furoate, a topical corticosteroid ointment.
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Topical application of 12 % ammonium lactate lotion is also effective in nevus comedonicus treatment.
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A combination of topical Calcipotriene 0.005% cream and topical Tazarotene 0.05% cream has also proven effective in removing nevus comedonicus.
Systemic Treatment:
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Systemic antibiotics (Tetracycline 500 mg orally twice daily or Doxycycline 100 mg orally twice daily) and intralesional steroids (Intralesional Kenalog 5–10 mg/cc) may be necessary for more severe lesions associated with infected nevus comedonicus.
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It has been observed that systemic administration of Isotretinoin (0.5–1.0 mg/kg) is effective in reducing nevus comedonicus. It is necessary to take into account the special restrictions on this medication due to its teratogenic and other adverse effects.
Surgery:
For bigger lesions, surgery might be necessary. Symptomatic relief can be achieved by draining cysts or abscesses and manually popping nevus comedonicus. This method may be used in conjunction with topical treatments to sustain progress.
Conclusion
Nevus comedonicus is an uncommon cutaneous disorder resulting from a developmental abnormality of the pilosebaceous apparatus. It commonly appears as black papules in the comedone distribution and can affect any area of the skin. They may manifest as an independent cutaneous disorder or a part of the syndrome known as nevus comedonicus syndrome. Even though the precise cause is still unknown, advances in genetic studies provide insight into the underlying pathways. Combining topical, systemic, and procedural treatments is necessary for effective management to improve the quality of life for those impacted.
