Psoriasis and psoriatic arthritis are interrelated heritable diseases, occurring with greater heritable frequency than rheumatoid arthritis, primary Sjögren syndrome and thyroid disease. Psoriasis affects 2–3% of the Caucasian population, and psoriatic arthritis affects up to 30% of those. Arthritis mutilans presents in about 5–16% of psoriatic arthritis cases, involves osteolysis of the DIP and PIP joints, and can include bone edema, bone erosions, and new bone growth. Most often psoriatic arthritis is seronegative for rheumatoid factor (occurring in only about 13% of cases), and has genetic risk factor overlap with ankylosing spondylitis with HLA-B27, IL-23R77, and IL-1, however, as of 2016, immunopathogenesis is unclear. Diagnosis
Enthesitis can assist in differentiating arthritis mutilans parent condition psoriatic arthritis from rheumatoid arthritis and osteoarthritis, with evidence in plain radiographs (x-rays) and MRI as periostitis, new bone formation, and bone erosions. Dactylitis, spondylitis and sacroiliitis are common with the parent condition psoriatic arthritis, but are not in rheumatoid arthritis. MRI bone edema scores are high in arthritis mutilans and correlate with radiographic measures of joint damage, although they may not correlate with disease activity. A source of significant pain, bone marrow edema (or lesions, using newer terminology), can be detected on MRI or with ultrasonography by signals of excessive water in bone marrow. Specifically, bone marrow edema can be detected within bone on T1-weighted images as poorly defined areas of low signal, with a high signal on T2-weighted fat-suppressed images.
Epidermolysis bullosa simplex (EBS) is a disorder resulting from mutations in the genes encoding keratin 5 or keratin 14.: 598 Blister formation of EBS occurs at the dermoepidermal junction. Sometimes EBS is called epidermolytic. Cause
Absence of keratin-5,14 since birth. Diagnosis
Classification
Epidermolysis bullosa simplex may be divided into multiple types:

Management
No cure for EB
Treat symptoms
Protect skin, stop blister formation, promote healing
Prevent complications
Necessary treatment: use oral and topical steroid for healing and prevent complication
Maintain cool environment, avoid overheating and decreases friction

See also
Epidermolysis bullosa
List of cutaneous conditions caused by mutations in keratins

References
Further reading

GeneReviews/NCBI/UW/NIH entry on Epidermolysis Bullosa Simplex


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