Coexistence of Dermatomyositis and Alopecia Areata: Insight into Pathogenesis

Sir,

A 9-year-old girl presented with heliotrope rash and gottron's papules since 1 year and difficulty in climbing stairs and combing hair since 6 months [Figures 1–3]. Three years back she developed a nonscarring bald patch which gradually progressed to involve the entire scalp and lateral two-thirds of eyebrows. Musculoskeletal examination revealed weakness and reduced power in muscles of the shoulder and pelvic girdle. There was no history of Raynaud's phenomenon or skin thickening.

Figure 1.

Heliotrope rash and aloplecia areata totalis with loss of lateral 2/3 of eyebrows

Figure 3.

Gottron's papules present on both knees

Figure 2.

Gottron's papules present on the interphalangeal joints and along the extensor tendons on the dorsum of both hands

Skin biopsy showed atrophic epidermis with focal basal layer vacuolization and sparse perivascular mononuclear cell infiltrate. Direct immunofluorescence (IF) was negative for IgG, IgM, and C3. Lactate dehydrogenase, creatine kinase, and creatine phosphokinase were raised. Electromyography showed myopathic pattern with fasciculations. Antinuclear antibody was positive by indirect immunofluorescence. PM-Scl was positive whereas ds-DNA was negative. Thyroid function tests were normal.

Diagnosis of juvenile dermatomyositis (DM) with alopecia areata (AA) was made, and methotrexate 12.5 mg weekly and prednisolone 2 mg/kg was started. The alopecia resolved within a month of starting therapy and there was gradual improvement in muscle power [Figure 4].

Figure 4.

Improvement in the aloplecia areata after 1 month of treatment

The patient had typical clinical, histologic, and electromyographic features of DM. The development of AA in our case and the close temporal association between the two disorders suggest that they may be etiologically linked.

Occurrence of two or more immune-mediated diseases simultaneously, although infrequent, has been documented. DM is associated with several autoimmune diseases, however, its association with AA has not been noted previously.

DM is an inflammatory myopathy characterized by cellular infiltrates in muscles and presence of circulating autoantibodies including several myositis-specific autoantibodies. The most frequent are anti-tRNA synthetase autoantibodies present in 25–30% of the patients. The levels of these autoantibodies correlate with disease activity supporting their role in pathogenesis.[1] Interestingly, circulating immune complexes containing them can trigger immune responses through activating interferon (IFN).[2]

An IFN- α signature has been demonstrated in muscles and peripheral blood in patients with DM.[3] IFNs are strong inducers of major histocompatibility complex (MHC) class I and II molecules. Muscle fibres do not express MHC class I in healthy individuals, however, they are present in muscles in patients with myositis. This leads to presentation of autoantigens to CD8 + T cells, which have direct toxic effects on muscle fibres, causing their necrosis and muscle weakness.[4]

Furthermore, IFN-α may be involved in the pathogenesis of AA as there are reports of AA that occurred after IFN-α 2b therapy.[5,6] Although the exact mechanism of hair loss is unclear, IFN-α may take part in the initiation of AA by inducing MHC class I expression on hair follicles. Moreover, IFN-α may modulate the production and activity of several cytokines such as IFN-γ, IL-1, IL-2, and IL6.[6]

Hair follicle is an immune privilege site lacking MHC class I expression. IFN-γ, is the key cytokine implicated in the pathogenesis of AA. It is strongly expressed in AA lesions and induces MHC class I molecules with subsequent activation of autoreactive CD8+ T cells and resultant hair loss.[7] Several factors increase production of IFN-γ in vivo, and in our patient circulating autoantibodies present due to coexisting DM may be the trigger.

Another possible explanation for the association of DM and AA is that the basal layer damage in DM may expose basement membrane zone antigens, leading to the formation of antibodies, with subsequent damage of the hair bulb and alopecia.

The association between DM and AA is hitherto undescribed. This rare association suggests common etiological linkage and emphasizes the need for further research to understand the etiopathogenesis of these immune-mediated diseases.

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Conflicts of interest

There are no conflicts of interest.