Lichen striatus is defined by:

The papules could be smooth, flat topped or scaly. The band of lichen striatus varies from a few millimeters to 1-- 2 cm wide and extends from a few centimeters to the complete length of the extremity. By and big, the papules are unilateral and single on an extremity along the lines of Blaschko.

Aside from the visible rash, granuloma annulare is usually asymptomatic. Sometimes the rash may burn or itch. People with granuloma annulare usually notice a ring of small, firm bumps (papules) over the backs of the forearms, hands or feet, often centered on joints or knuckles. The bumps are caused by the clustering of T cells below the skin. These papules start as very small, pimple looking bumps, which spread over time from that size to dime, quarter, half-dollar size and beyond. Occasionally, multiple rings may join into one. Rarely, granuloma annulare may appear as a firm nodule under the skin of the arms or legs. It also occurs on the sides and circumferential at the waist and without therapy can continue to be present for many years. Outbreaks continue to develop at the edges of the aging rings.

Linear arrangements of these papules is common (referred to as a Koebner phenomenon), especially on the forearms, but may occasionally be grouped, though not confluent, on flexural areas. Generally, the initial lesions are localized, and remain so, to the chest, abdomen, glans penis, and flexor aspects of the upper extremities; however, less commonly, the disease process can (1) be strictly isolated to the palms and soles, presenting with many hyperkeratotic, yellow papules that may coalesce into plaques that fissure or “...sometimes a non-specific keratoderma resembling chronic eczema,” or (2) become more widespread, with papules widely distributed on the body—the extensor surfaces of the elbows, wrists, and hands, folds of the neck, submammary region in females, groin, thighs, ankles, and feet—and fusing into erythematous, minimally scaled plaques, with reddness that develops tints of violet, brown, and yellow.

The histology of lichen nitidus is significant for a "...localized granulomatous lymphohistiocytic infiltrate in an expanded dermal papilla with thinning of overlying epidermis and downward extension of the ridges at the lateral margin of the infiltrate, producing a typical 'claw clutching a ball' picture..."

A papule (/ˈpæpjuːl/) is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm. It can be brown, purple, pink or red in color, and can cluster into a papular rash. Papules may open when scratched and become infected and crusty. Larger non-blisterform elevated lesions may be termed nodules.

Papules may have different shapes and are sometimes associated with other features such as crusts or scales.

Lichen striatus (also known as blaschko linear acquired inflammatory skin eruption and linear lichenoid dermatosis) is a rare skin condition that is seen primarily in children, most frequently appearing ages 5–15. It consists of a self-limiting eruption of small, scaly papules.

There are many skin diseases which develop papules, such as Lichen planus, a skin disease which classically forms polygonal, purple papules.

Darier disease affects both men and women and is not contagious. The disease often starts during or later than the teenage years, typically by the third decade. Short stature is common. The symptoms of the disease are thought to be caused by an abnormality in the desmosome-keratin filament complex leading to a breakdown in cell adhesion.

Worldwide prevalence is estimated as between 1: 30,000 and 1: 100,000. Case studies have shown estimated prevalence by country to be 3.8: 100,000 in Slovenia, 1: 36,000 in north-east England, 1: 30,000 in Scotland, and 1: 100,000 in Denmark

It most commonly affects the chest, neck, back, ears, forehead, and groin, but may involve other body areas. The rash associated with Darier's disease often has a distinct odor. Palms & soles may become thickened, intra oral papules can be found. Finger nails become fragile and this helps in diagnosis of the disease. The rash can be aggravated by heat, humidity, and exposure to sunlight. In some cases, sunlight makes it better, especially in the forehead.

Minor forms of the disease are the most common, and may remain undiagnosed throughout life. These consist mainly of minor rashes without odor that are aggravated by heat, humidity, stress and sunlight. Poorly formed fingernails containing vertical striations are diagnostic.

A recent study examined neuropsychiatric conditions in a non-random sample of 100 British individuals assessed as having DAR. There were high lifetime rates for mood disorders (50%), including depression (30%), bipolar disorder (4%), suicidal thoughts (31%) and suicide attempts (13%), suggesting a possible common genetic link. Scattered case studies also suggest a possible link to learning disorders (not yet confirmed).

Darier's disease (DAR), also known as Darier disease, Darier–White disease, Dyskeratosis follicularis and Keratosis follicularis, is an autosomal dominant disorder discovered by French dermatologist Ferdinand-Jean Darier. Darier's is characterized by dark crusty patches on the skin, sometimes containing pus. The crusty patches are also known as keratotic papules, keratosis follicularis or dyskeratosis follicularis.

Mild forms of the disease are the most common, consisting solely of skin rashes that flare up under certain conditions such as high humidity, high stress or tight-fitting clothes. Even in mild forms, short stature combined with poorly formed fingernails containing vertical striations are diagnostic.

Acrokeratoelastoidosis of Costa (also known as "Keratoelastoidosis marginalis") is a familial condition characterized by multiple keratotic papules on the dorsum of the hands and feet, palms, soles, in which electron microscopy shows rarified, abnormal elastic tissue.

It was characterized in 1953.

Treatments such as liquid nitrogen, salicylic acid, tretinoin, and prednisone have been tried, though with limited success.

Granuloma annulare is a fairly rare, chronic skin condition which presents as reddish bumps on the skin arranged in a circle or ring. It can initially occur at any age and is four times more common in females.

Granulosis rubra nasi is a rare familial disease of children, occurring on the nose, cheeks, and chin, characterized by diffuse redness, persistent hyperhidrosis, and small dark red papules that disappear on diascopic pressure.

Nevus comedonicus (also known as a "comedo nevus") is characterized by closely arranged, grouped, often linear, slightly elevated papules that have at their center keratinous plugs resembling comedones.

Nevus spilus (also known as speckled lentiginous nevus and zosteriform lentiginous nevus) is a skin lesion that presents as a light brown or tan macule, speckled with smaller, darker macules or papules.

Lichen aureus (also known as "lichen purpuricus") is a skin condition characterized by the sudden appearance of one or several golden or rust-colored, closely packed macules or lichenoid papules.

Perforating granuloma annulare is a skin condition of unknown cause, usually appearing on the dorsal hands, presenting as papules with a central keratotic core.

Lichen scrofulosorum (also known as "Tuberculosis cutis lichenoides") is a rare tuberculid that presents as a lichenoid eruption of minute papules in children and adolescents with tuberculosis. The lesions are usually asymptomatic, closely grouped, skin-colored to reddish-brown papules, often perifollicular and are mainly found on the abdomen, chest, back, and proximal parts of the limbs. The eruption is usually associated with a strongly positive tuberculin reaction.

Of the three tuberculids, the incidence of lichen scrofulosorum was found to be the lowest (2%) in a large study conducted in Hong Kong. This highlights its rarity and significance as an important marker of undetected tuberculosis.

CGPD is characterized by the presence of small, raise, dome-shape papules primarily distributed around the mouth, eyes, and nose. Affected children may also have papules on the ears, eyelids, cheeks, forehead, and nose. CGPD skin lesions affecting areas of the skin other than the face are rare.

Presentation includes telangiectasia, acanthosis, and hyperkeratosis.

Presentation can be solitary or systemic.

Papular mucinosis of infancy (also known as "Cutaneous mucinosis of infancy") is a skin condition caused by fibroblasts producing abnormally large amounts of mucopolysaccharides, characterized by skin-colored or translucent papules.

CGPD is known to be a temporary skin disease with a benign course. The skin papules typically resolve after a few months to a few years. After CGPD resolves, the skin may return to normal without scarring or may have small atrophic depressions with collagen loss, milia, or small pit-like scars.

Disseminate and recurrent infundibulofolliculitis or Disseminate and Recurrent Infundibular Folliculitis also called Hitch and Lund disease, is a rare itchy follicular skin condition presents with irregularly shaped papules pierced by hair, mildly pruritic at times, and is chronic with recurrent exacerbations.

In both healthy and immunocompromised hosts, Majocchi's granuloma often presents as nodules and papules on areas that are most exposed to mechanical abuse—wear and tear—such as the upper and lower extremities. Patients will complain about papules, pustules, or even plaques and nodules at the site of infection. The papules will be pink-red and will be located in a perifollicular location. Hair shafts can be easily removed from the pustules and papules. Itching is also very common. Firm or fluctuant subcutaneous nodules or abscesses represent a second form of MG that is generally observed in immunosuppressed hosts. Nodules may develop in any hair-bearing part of the body but are most often observed on the forearms, hands, and legs of infected individuals. Involvement of the scalp and face is rarely observed. Lesions start as solitary or multiple well-circumscribed perifollicular papulopustules and nodules with or without background erythema and scaling. In rare circumstances, the lesions may have keloidal features.

Acral persistent papular mucinosis is a skin condition caused by fibroblasts producing abnormally large amounts of mucopolysaccharides, characterized by bilaterally symmetrical, flesh-colored papules localized to the hands and wrists.

In some instances nodular angiokeratomas can produce necrotic tissue and valleys that can harbor fungal, bacterial and viral infections. Infections can include staphylococcus. If the lesion becomes painful, begins draining fluids or pus, or begins to smell, consult a physician. In these instance a doctor may recommend excision and grafting.