How to diagnose a skin condition from a picture?

Diagnosing Skin Conditions from Clinical Images

A single photograph is insufficient for accurate diagnosis of skin conditions and should always be supplemented with clinical examination, patient history, and potentially additional diagnostic techniques such as dermoscopy or biopsy.

Limitations of Photographic Diagnosis

• Photographs alone have significant diagnostic limitations, with studies showing that even highly trained dermatologists differ significantly in their interpretations of skin images, with average reproducibility and reliability of only approximately 85% 1
• The British Medical Association warns that photographic evaluation alone is not sufficient for definitive diagnosis, as cases of melanoma mimicking benign conditions like seborrheic keratosis have been documented 2
• Primary care physicians show limited accuracy in diagnosing skin conditions from photographs, with one study showing correct diagnosis in only 72% of cases despite high confidence in their diagnoses 3

Recommended Diagnostic Approach

Initial Assessment

• Perform a systematic physical examination with careful description of:
  • Component of skin affected
  • Primary lesion characteristics
  • Extent and distribution
  • Secondary changes
  • Skin color, moisture, turgor, texture, and temperature 4

Documentation of Key Features

• Record any changes in size, shape, color, diameter (especially ≥7mm), inflammation, sensory changes, and crusting or bleeding 2
• Document the distribution pattern and anatomic location of lesions 4
• Note any mucous membrane involvement which may indicate serious conditions like Stevens-Johnson syndrome 5

Advanced Diagnostic Techniques

• For uncertain diagnoses, consider:
  • Reflectance confocal microscopy (RCM) for specialized settings, though this has limitations for very thickened or ulcerated lesions 2, 5
  • Skin biopsy with complete excision and a narrow rim (2mm) of normal skin for suspected malignant lesions 2, 6

Special Considerations for Specific Conditions

For Suspected Cutaneous Tumors

• When using RCM, ensure good-quality mosaics at multiple levels:
  • Corneal layer
  • Upper mid epidermis
  • Lower epidermis
  • Dermoepidermal junction
  • Papillary dermis
  • Papillary/reticular dermis 5

For Suspected Inflammatory Conditions

• Document any mucosal site involvement (eyes, mouth, nose, genitalia) 5
• Record symptoms indicating respiratory tract involvement: cough, dyspnoea, bronchial hypersecretion 5
• Note symptoms of bowel involvement: diarrhoea and abdominal distension 5

Pitfalls to Avoid

• Relying solely on visual assessment without clinical context can lead to misdiagnosis, especially for conditions that mimic each other 2, 6
• Nondermatologists perform poorly in diagnosis and treatment of skin disease, with studies showing correct diagnosis rates of only 43-52% among internal medicine physicians 7
• Automated systems using artificial intelligence show promise (97.5% accuracy in one study) but require standardized image acquisition and should be used as decision support rather than replacement for clinical judgment 8

When to Refer to Dermatology

• For lesions with concerning features (changing size/shape/color, bleeding, ulceration) 2
• When initial treatment fails to improve the condition 7
• For any suspected malignancy or rare dermatological condition 6
• When biopsy is being considered, as dermatologists are more judicious in ordering biopsies 7