Female with Skin rash and difficulty in sitting and squatting with knees, back ache

Discussion

Sudden worsening of the bilateral knee pain (from past 15 days) was reported in the 58-yr-old female patient. The non-inflammatory joint involvement appears, but with a skin lesion suggestive of psoriasis vs allergic rashes (Eczema).  Laboratory findings revealed elevated serum Ig E and normal inflammatory parameters (ESR and CRP). Her X -ray of knee showed sclerosis with reduced joint space and marginal osteophytes consistent with osteoarthritis.

The probable diagnoses are osteoarthritis with allergic eczema, psoriatic arthritis, rheumatoid arthritis with skin lesion due to allergic rashes, or connective tissue disease. In a patient with arthritis and skin rashes, it is crucial to give due importance to skin rashes, especially when considering a probability of psoriatic arthritis. The criteria considered for differentiating psoriasis from eczema are given in table 2.

Table 2: Criteria considered for differentiating between psoriasis and eczema

Elevated Ig E suggests a tendency to develop atopy and allergy and it does not confirm the diagnosis of allergy.^1, 2 Presence of antigen-specific IgE, which indicates the possibility of diagnosis, is more specific and sensitive compared to total IgE. In the present case, the lesions appear like eczematous rashes and elevated IgE suggests the possibility of allergy. The opinion from dermatologist opinion was eczema. This suggests the skin lesion is independent of arthritis.

X-ray evaluation of knee joint suggests osteoarthritis (OA).  In an elderly at the age above 50, knee pains with no morning stiffness, normal ESR and CRP, and RF negative add to the clinical possibility of knee OA. In such cases, there could be a possibility of co-existing inflammatory arthritis with knee osteoarthritis.  Hence it is important to assess the presence of other factors responsible for joint pain in a patient who present with sudden deterioration of pain.

Although the patient had dry mouth, it did not interfere in her day-to-day. The examination of oral cavity, normal salivary pool, and evidence of no involvement of eye will help to validate the oral symptom.

Normal inflammatory parameters and negative RF and ANA suggest the condition as osteoarthritis and the presence of elevated serum IgE suggests the rashes to be eczema.

Final diagnosis:

Osteoarthritis with eczema

Key learning points

• For the diagnosis of arthritis, due consideration should be given to all additional features.
• Certain presentations like oral symptoms and skin rashes may not assist in diagnosis.
• Although OA is the common in elderly and can cause exacerbation of pain with swelling, it is significant to consider alternative diagnosis.

References

1. Rook's Textbook of Dermatology. Clinical Immunology allergy and photo immunology Author G P Spickett and T Schwarz :Eds  Burns, Tony, Rook, Arthur pp 13.16 p weily Blackwell. E –edition.
2. Altman R, Asch E, Bloch D, Bole G, Borenstein D, Brandt K, et al. Development of criteria for the classification and reporting of osteoarthritis: classification of osteoarthritis of the knee. Arthritis Rheum. 1986 Aug;29(8):1039-49.