1,838 articles
PENS syndrome
PENS syndrome (papular epidermal nevus with "skyline" basal cell layer syndrome) is a rare neurocutaneous disorder: congenital hyperkeratotic papules with a palisaded basal cell layer, with neurological abnormalities in about 50% of cases.
Perforating dermatoses
Perforating dermatoses (acquired perforating dermatosis, reactive perforating collagenosis, Kyrle disease, perforating folliculitis, elastosis perforans serpiginosa) are skin disorders marked by transepidermal elimination of collagen or elastin, mainly in diabetes and chronic kidney disease.
Periarthritis of wrist
Periarthritis of wrist (ICD-11 FB55.2) is inflammation of tissues around the wrist joints, an enthesopathy mapping to ICD-10 M77.2, covering tenosynovitis, de Quervain disease, and acute calcific periarthritis.
Periodontal Ehlers-Danlos syndrome
Periodontal Ehlers-Danlos syndrome (pEDS, formerly EDS type VIII) is an ultra-rare autosomal dominant connective tissue disorder caused by gain-of-function variants in C1R or C1S, causing severe childhood periodontitis, lack of attached gingiva, pretibial plaques, and premature tooth loss.
Perioral dermatitis
Perioral dermatitis, also called periorificial dermatitis (POD), is a chronic acneiform rash around the mouth, nose, or eyes, mainly in women 20–45, strongly linked to topical corticosteroids and treated with zero therapy and tetracyclines.
Periorbital dark circles
Periorbital dark circles (periorbital hyperpigmentation, POH, ICHOR): bilateral darkened eyelid skin from pigment, visible vasculature, or structural shadowing; treated by cause with topicals, lasers, fillers, or surgery.
Peripheral primitive neuroectodermal tumor
Peripheral primitive neuroectodermal tumor (pPNET, PPNET, ICD-O 9364) is a rare aggressive small round cell sarcoma of bone or soft tissue outside the CNS, part of the Ewing family of tumors with the t(11;22) EWS-FLI1 fusion, peaking in the second decade.
Peripheral spondyloarthritis
Peripheral spondyloarthritis (pSpA) is the peripheral-joint form of spondyloarthritis, marked by arthritis, enthesitis, and dactylitis, classified by 2011 ASAS criteria and distinguished from axial SpA and psoriatic arthritis sine psoriase.
Pes cavus
Pes cavus (high arch feet) is a multiplanar foot deformity with an abnormally raised medial longitudinal arch, usually neuromuscular (often Charcot-Marie-Tooth disease), causing pain and ankle instability; treated with custom foot orthoses or surgery.
Petechiae
Petechiae are pinpoint, round spots of bleeding under the skin or mucous membranes, caused by blood escaping broken capillaries, that do not blanch when pressed.
Phakomatosis pigmentokeratotica
Phakomatosis pigmentokeratotica (PPK), a rare epidermal nevus syndrome combining nevus sebaceus and speckled lentiginous nevus with extracutaneous anomalies, caused by a postzygotic HRAS mutation, prevalence under 1 in 1,000,000.
Phakomatosis pigmentovascularis
Phakomatosis pigmentovascularis (PPV), also phacomatosis pigmentovascularis, is a rare congenital disorder combining a vascular nevus (port-wine stain) with a pigmentary nevus, caused by mosaic GNAQ/GNA11 mutations, with types cesioflammea, spilorosea, and cesiomarmorata.
Phalangeal microgeodic syndrome
Phalangeal microgeodic syndrome (phalangeal osteolysis) is a rare, self-limited cold-associated bone disorder of children's fingers, with small sclerotic-lined osteolytic phalangeal lesions, winter onset, and spontaneous resolution within months.
Phossy jaw
Phossy jaw (phosphorus necrosis of the jaw) was an occupational osteonecrosis of match-factory workers exposed to white phosphorus fumes; about 11% of the exposed developed it, it killed roughly 20%, and it ended after the 1906 Berne Convention.
Photo-allergic contact dermatitis
Photo-allergic contact dermatitis (PACD, photoallergic eczema) is a type IV hypersensitivity skin reaction to a light-activated contact allergen, mainly sunscreens and topical NSAIDs, diagnosed by photopatch testing and distinguished from phototoxic dermatitis by delayed onset and sensitization.
Photoaging of the skin
Photoaging of the skin: UV radiation-driven premature skin aging, mainly UVA (95% of terrestrial UV) and UVB, causing wrinkles, lentigines, solar elastosis, immunosuppression; treated with sunscreens and topical retinoids.
Phymatous rosacea
Phymatous rosacea, formerly subtype 3, is rosacea with skin thickening from sebaceous hyperplasia and fibrosis, most often rhinophyma of the nose; it is a diagnostic phenotype treated mainly with surgery and lasers.
Phytophotodermatitis
Phytophotodermatitis, also called lime disease, is a non-immunologic phototoxic skin reaction caused by furocoumarins (psoralens) from plants such as limes, figs, hogweed, and celery, activated by UVA sunlight, causing streaky blisters and lasting hyperpigmentation.
Piebaldism
Piebaldism (piebald trait, PBT) is a rare autosomal dominant disorder of melanocyte development caused mainly by KIT mutations, producing congenital stable white skin patches and a white forelock in 80–90% of cases.
Pigeon toe
Pigeon toe (intoeing) is a common childhood gait pattern with feet turned inward, caused by metatarsus adductus, internal tibial torsion, or femoral anteversion; it usually self-corrects by age 8 without treatment.
Pigmented villonodular synovitis
Pigmented villonodular synovitis (PVNS), now called tenosynovial giant cell tumor, is a rare benign but locally aggressive proliferation of the joint lining, most often affecting the knee.
Pili bifurcati
Pili bifurcati (ORPHA:720, ICD-10 L67.8) is a rare hair shaft dysplasia with segmental shaft duplication: two cuticle-covered branches fuse back into one shaft, caused by transient papilla-tip duplication during anagen.
Pili gemini
Pili gemini (pili multigemini), ORPHA:79492, is a rare hair follicle abnormality where the follicular papilla splits in anagen so multiple hair shafts emerge from one follicular opening, mostly in men's beards; ICD-10 L67.8.
Pili torti
Pili torti (twisted hair) is a rare hair shaft disorder with flattened shafts twisted 180 degrees, causing brittle, spangled, easily broken hair; isolated, syndromic (Menkes, Bjornstad), or acquired.
Pilomatrix carcinoma
Pilomatrix carcinoma, also called malignant pilomatricoma, is a rare malignant skin tumor of hair follicle cells, usually a firm nodule on the head or neck of older adults.
Pilomatrixoma
Pilomatrixoma (calcifying epithelioma of Malherbe, pilomatricoma) is a benign hair follicle matrix tumor, common in children on the head and neck, linked to CTNNB1/Wnt mutations, treated by excision with low recurrence.
Pilonidal disease
Pilonidal disease, also called pilonidal sinus or jeep disease, is an acquired infection of the natal cleft caused by penetrating loose hairs, affecting young adults; treated by drainage, off-midline flap surgery, and hair removal.
Pilosebaceous hamartoma
Pilosebaceous hamartoma (ICD-11 LC01) is a benign, tumor-like malformation of the hair follicle and sebaceous gland. Subtypes include basaloid follicular hamartoma and folliculosebaceous cystic hamartoma, first described by Kimura in 1991.
Pimple
A pimple, also called a zit, is a small inflamed skin lesion that forms when a pore clogs with oil, bacteria, and dead skin cells; pimples are the lesions of acne.
Pitted keratolysis
Pitted keratolysis (keratolysis plantare sulcatum), a superficial bacterial infection of the soles causing 1–3 mm pits and foul odor, caused by Corynebacteria and related Gram-positive bacteria, treated with topical antibiotics.