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Juvenile Dermatomyositis anti-NXP2 with Capillaroscopic Improvement

Name: Juvenile Dermatomyositis anti-NXP2 with Capillaroscopic Improvement
Creator: Clara Udaondo

Juvenile Dermatomyositis (anti-NXP2+)Early Scleroderma-Like Pattern with Treatment ResponseModerate to Severe

A 12-year-old girl with muscle weakness, markedly elevated CPK, and no skin disease, followed with two capillaroscopies during treatment response.

AuthorClara Udaondo

Clinical context

The patient presented with several weeks of shoulder and pelvic girdle weakness, without skin involvement or other symptoms. Laboratory testing showed CPK elevation up to 8000 U/L, lymphopenia, thrombocytopenia, and low-titer positive ANA. Whole-body MRI showed muscle edema in the girdles. The initial myositis panel was negative, so the early scleroderma-like capillaroscopy pattern helped support the diagnosis of juvenile dermatomyositis despite the absence of skin disease or specific autoantibodies. An extended panel later detected anti-NXP2 antibodies. Treatment was started with hydroxychloroquine, mycophenolate mofetil, and intravenous immunoglobulin, followed by clinical improvement and CK reduction.

Capillaroscopy

The June 2024 capillaroscopy showed an early scleroderma-like pattern compatible with juvenile dermatomyositis, including reduced density, frequent enlarged capillaries, sparse giant capillaries, and hemorrhages. The December 2024 follow-up showed disappearance of giant capillaries and evolution toward a non-specific pattern, with improved capillary density.

Key Capillaroscopic Findings

Initial reduced density (5.83/mm) with frequent enlarged capillaries (68.8%)
Initial sparse giant capillaries (2.6%) and hemorrhages
Follow-up density improved to 6.72/mm, with disappearance of giant capillaries

Initial study

Follow-up study

Longitudinal Capillaroscopic Comparison

June 2024 → December 2024

Capillary density (N/mm)5.83 (Reduced)→6.72 (Improved)

Giant capillaries2.6%→0%

HemorrhagesPresent (0.17/mm)→Present, mild (0.20/mm)

Enlarged capillaries (%)68.8%→38.1%

2 capillaroscopies