The skin is often considered the “window” into the body and can be the first sign of many internal diseases. Here is a list:
Endocrine Disorders:
- Diabetes: Acanthosis nigricans, diabetic dermopathy, necrobiosis lipoidica, digital sclerosis, bullous diabeticorum (diabetic blisters), eruptive xanthomatosis.
- Thyroid Disorders: Myxedema (in hypothyroidism), pretibial myxedema (in Graves’ disease), thyroid acropachy.
- Addison’s disease: Hyperpigmentation, particularly in sun-exposed areas.
- Cushing’s syndrome: Striae (stretch marks), thinning skin, easy bruising, purpura, telangiectasia, acne, hirsutism.
Liver Diseases:
- Cirrhosis: Jaundice, spider angiomas, palmar erythema, Terry’s nails (white nail beds), xanthelasma.
- Primary biliary cholangitis: Pruritus, xanthomas.
- Hemochromatosis: Bronze diabetes (increased skin pigmentation), porphyria cutanea tarda.
Kidney Disease:
- Uremic pruritus, xerosis, uremic frost, half-and-half nails (nails with two-toned coloring).
Connective Tissue Diseases:
- Systemic lupus erythematosus: Malar rash, discoid rash, lupus panniculitis, vasculitis, photosensitivity.
- Dermatomyositis: Heliotrope rash (purple rash on eyelids), Gottron’s papules, shawl sign, V-sign, mechanic’s hands.
- Scleroderma: Skin tightening and thickening, Raynaud’s phenomenon, telangiectasias, salt-and-pepper skin, calcinosis cutis.
- Rheumatoid arthritis: Rheumatoid nodules, livedo reticularis, vasculitis, Felty’s syndrome (associated with leg ulcers).
Gastrointestinal Disorders:
- Celiac disease: Dermatitis herpetiformis.
- Inflammatory bowel disease: Erythema nodosum, pyoderma gangrenosum, aphthous ulcers, Sweet’s syndrome.
- Whipple’s disease: Hyperpigmentation.
- Peutz-Jeghers syndrome: Melanotic macules of the lips, buccal mucosa, and digits.
Cardiovascular Diseases:
- Infective endocarditis: Osler’s nodes (painful red nodules on fingers and toes), Janeway lesions (non-painful red lesions on palms and soles), petechiae, splinter hemorrhages.
- Peripheral artery disease: Atrophic skin changes, hair loss, ulcers, gangrene.
Hematological Disorders:
- Polycythemia vera: Aquagenic pruritus, erythromelalgia.
- Essential thrombocythemia: Erythromelalgia.
- Leukemia: Leukemia cutis, Sweet’s syndrome.
- Multiple myeloma: Amyloidosis.
Infectious Diseases:
- HIV/AIDS: Seborrheic dermatitis, Kaposi’s sarcoma, oral hairy leukoplakia, herpes zoster, molluscum contagiosum, prurigo nodularis.
- Hepatitis C: Lichen planus, porphyria cutanea tarda, cryoglobulinemia.
- Tuberculosis: Lupus vulgaris, scrofuloderma.
- Syphilis: Chancre (primary syphilis), condyloma lata, rash (secondary syphilis), gummas (tertiary syphilis).
This list is not exhaustive, and many internal diseases can manifest with nonspecific dermatologic signs, such as generalized pruritus or erythema.
Here’s a list of some common associations:
- Acanthosis nigricans: Insulin resistance, obesity, type 2 diabetes, certain cancers.
- Candidiasis (Candida skin infections): Diabetes, immunosuppression, long-term antibiotics or corticosteroid therapy.
- Psoriasis: Psoriatic arthritis, metabolic syndrome, cardiovascular diseases, inflammatory bowel disease.
- Xanthomas: Hyperlipidemia, high cholesterol or triglycerides.
- Erythema nodosum: Sarcoidosis, inflammatory bowel diseases, streptococcal infections, tuberculosis, histoplasmosis.
- Necrobiosis lipoidica: Diabetes mellitus.
- Jaundice: Liver disease, hepatitis, cirrhosis.
- Spider angiomas: Liver disease, cirrhosis, pregnancy.
- Dermatomyositis: Underlying malignancy (ovarian, lung, pancreatic, stomach, colorectal cancers).
- Granuloma annulare: Diabetes, thyroid disease.
- Porphyria cutanea tarda: Liver disease, alcohol use, hepatitis C, HIV.
- Vitiligo: Autoimmune conditions (thyroid disease, type 1 diabetes, Addison’s disease).
- Scleroderma: Pulmonary hypertension, interstitial lung disease, Raynaud’s phenomenon.
- Lupus erythematosus: Systemic lupus affecting multiple organs.
- Pyoderma gangrenosum: Inflammatory bowel diseases, arthritis, hematological disorders.
- Cutaneous vasculitis: Lupus, rheumatoid arthritis, Sjögren’s syndrome.
- Pigmented purpuric dermatoses: Venous hypertension, diabetes, medication reactions.
- Hemochromatosis (bronze diabetes): Diabetes, liver disease.
- Urticaria (hives): Thyroid disease, autoimmune conditions.
- Angioedema: Allergic reactions, certain medications, hereditary conditions.
- Acrodermatitis enteropathica: Zinc deficiency.
- Lichen Planus: Hepatitis C, certain medications.
- Necrolytic migratory erythema: Glucagonoma (pancreatic tumor).
- Peutz-Jeghers syndrome: Gastrointestinal polyposis, increased cancer risk.
- Bullous pemphigoid: Neurological diseases (multiple sclerosis, Parkinson’s disease).
- Erythema multiforme: Herpes simplex virus, medications.
- Actinic keratosis: Sun-damaged skin, squamous cell carcinoma precursor.
- Sweet’s syndrome: Infections, hematologic malignancies, medication reactions.
- Pellagra (niacin deficiency): Poor niacin diet, malabsorption conditions.
- Rubeosis facei (facial plethora): Cushing’s syndrome, high corticosteroid levels.
- Ichthyosis: Hodgkin’s lymphoma (acquired ichthyosis), thyroid disorders.
- Hyperpigmentation: Addison’s disease, hemochromatosis, medication side effects.
- Cutis laxa: Ehlers-Danlos syndrome, Marfan syndrome, inflammatory processes.
Systemic diseases often have associated skin manifestations, which can serve as important clues for diagnosis. Here is a list of some notable systemic diseases and their classical skin manifestations:
- Lupus Erythematosus
- Skin Manifestation: Malar rash (butterfly rash) on the face, discoid rash, photosensitivity, oral ulcers.
- https://dermnetnz.org/topics/systemic-lupus-erythematosus
- Scleroderma (Systemic Sclerosis)
- Skin Manifestation: Thickening and tightening of the skin, particularly on the fingers (sclerodactyly), and facial skin.
- https://dermnetnz.org/topics/systemic-sclerosis
- Dermatomyositis
- Skin Manifestation: Heliotrope rash (purple or violet rash) on upper eyelids, Gottron’s papules on the knuckles, shawl sign (rash on shoulders and back).
- https://dermnetnz.org/topics/adult-onset-dermatomyositis
- Rheumatoid Arthritis
- Skin Manifestation: Rheumatoid nodules, vasculitic lesions.
- https://dermnetnz.org/topics/rheumatoid-arthritis-and-the-skin
- Psoriasis
- Skin Manifestation: Silvery, scaly plaques on the skin, often on the elbows, knees, and scalp.
- https://dermnetnz.org/topics/psoriasis
- Inflammatory Bowel Disease (Crohn’s Disease and Ulcerative Colitis)
- Skin Manifestation: Erythema nodosum, pyoderma gangrenosum.
- https://dermnetnz.org/topics/erythema-nodosum
- Diabetes Mellitus
- Skin Manifestation: Diabetic dermopathy (shin spots), necrobiosis lipoidica diabeticorum, acanthosis nigricans.
- https://dermnetnz.org/topics/skin-problems-associated-with-diabetes-mellitus
- Addison’s Disease
- Skin Manifestation: Hyperpigmentation, especially in sun-exposed areas, and at pressure points, joints, and skin creases.
- https://dermnetnz.org/topics/addison-disease
- Sarcoidosis
- Skin Manifestation: Lupus pernio, erythema nodosum, maculopapular eruptions.
- Systemic Lupus Erythematosus (SLE)
- Skin Manifestation: Malar rash, discoid rash, photosensitivity.
- Mixed Connective Tissue Disease (MCTD)
- Skin Manifestation: Features of lupus, scleroderma, and dermatomyositis.
- Polymyositis
- Skin Manifestation: Although primarily a muscle disease, may have dermatomyositis-like skin features.
- Celiac Disease
- Skin Manifestation: Dermatitis herpetiformis.
- Porphyria
- Skin Manifestation: Photosensitivity, blisters, and scarring, particularly on the face and hands.
- HIV/AIDS
- Skin Manifestation: A variety of manifestations including Kaposi’s sarcoma, oral hairy leukoplakia, and various types of dermatitis.
- Lyme Disease
- Skin Manifestation: Erythema migrans (a red rash often in a bull’s-eye pattern).
- Syphilis
- Skin Manifestation: Various rashes, including the well-known palmar and plantar involvement in secondary syphilis.
- Graves’ Disease
- Skin Manifestation: Pretibial myxedema, characterized by thickening of the skin on the lower legs, and Graves’ dermopathy.
- Rheumatic Fever
- Skin Manifestation: Erythema marginatum, a distinctive rash that appears as rings on the trunk and inner aspects of the limbs.
- Hemochromatosis
- Skin Manifestation: Bronze diabetes, characterized by a slate-gray to bronze hyperpigmentation of the skin.
- Hyperthyroidism and Hypothyroidism
- Skin Manifestation: In hyperthyroidism, skin can be warm, moist, and smooth. In hypothyroidism, skin can become dry, thick, and coarse.
- Cushing’s Syndrome
- Skin Manifestation: Thin skin that bruises easily, striae (stretch marks), often purple and wide.
- Wilson’s Disease
- Skin Manifestation: Kayser-Fleischer rings (copper deposits) in the cornea, and a sunflower cataract.
- Polycythemia Vera
- Skin Manifestation: Plethora (ruddy complexion) and pruritus (especially after a hot bath).
- Endocarditis
- Skin Manifestation: Janeway lesions (painless erythematous lesions on palms and soles), Osler’s nodes (painful nodules on finger pads), petechiae.
- Chronic Kidney Disease
- Skin Manifestation: Pallor (from anemia), uremic frost insevere cases, and pruritus.
- Liver Cirrhosis
- Skin Manifestation: Palmar erythema, spider angiomas (small red or purple spider-like vessels on the skin), jaundice.
- Lichen Planus
- Skin Manifestation: This inflammatory condition, linked with hepatitis C, manifests as purple, pruritic, polygonal papules.
- Sjögren’s Syndrome
- Skin Manifestation: Dry skin (xerosis), annular erythematous rashes.
- Tuberous Sclerosis
- Skin Manifestation: Ash-leaf spots (white macules), angiofibromas, shagreen patches (thick, leathery skin).
- Mastocytosis
- Skin Manifestation: Urticaria pigmentosa (brownish lesions that might itch and turn into hives).
- Kawasaki Disease
- Skin Manifestation: Polymorphous rash, strawberry tongue, and erythema of the palms and soles.
- Ehlers-Danlos Syndrome
- Skin Manifestation: Hyperextensible skin, easy bruising, atrophic scarring.
- Amyloidosis
- Skin Manifestation: Waxy thickening of the skin, easy bruising, purpura around the eyes.
- Xanthomatosis (associated with various lipid disorders)
- Skin Manifestation: Xanthomas (yellowish cholesterol-rich material) on the skin, especially around the joints and tendons.
- Pellagra (Niacin Deficiency)
- Skin Manifestation: Photosensitive dermatitis, scaling, and redness particularly on areas exposed to sunlight.
- Pernicious Anemia
- Skin Manifestation: Pale skin, vitiligo, and smooth tongue (atrophic glossitis).
These skin manifestations are integral components of the clinical picture in many systemic diseases. However, it is crucial to consider them in the broader context of the patient’s overall clinical presentation and to conduct appropriate investigations to reach an accurate diagnosis.