A report describes a case of a 60-year-old woman who presented to the dermatology clinic with a history of gastroesophageal reflux disease, hypertension, migraines, seizure disorder, Sjogren disease, swelling of the lower portion of the leg and chronic hyponatremia. She showed dusky red-to-bluish discoloration and swelling of the hands, which worsened by cold exposure and associated with red papules and macules on fingers, periungual erythema and edema, nail dystrophy and fissuring of the fingertips. She initially started hydroxychloroquine treatment, which caused an eczematous total body rash and thus was discontinued. Quinacrine treatment also resulted in a similar skin eruption.

Erythema and scale developed on the patients forehead, malar area, and scalp pruritus. She started methotrexate treatment (25 mg weekly), which improved all symptoms. However, a few days later, she experienced increased seizure episodes, stomach upset and diarrhea.

Thus, she received mycophenolate mofetil treatment with a maximum dose of 3000 mg/day. However, it caused worsening of her hand swelling, erythema and swelling of her feet, legs and abdomen. Treatment with methotrexate was started again with careful monitoring, along with pentoxifylline 400 mg 3 times/day for anti-inflammatory effect. She showed some improvement in her skin symptoms and swelling of her hand and lower portion of the leg while on 20 mg/week of methotrexate. Her cutaneous and systemic response to methotrexate refrained from adding medications for dermatomyositis (DM).

She was taking salt tablets for chronic hyponatremia (baseline serum sodium of 129 mmol/L) associated with lightheadedness and mild intermittent leg swelling for nearly a decade. However, the treatment with methotrexate worsened this problem. She also developed diffuse anasarca in the superficial subcutaneous fat on the abdominal and pelvic.

Her antidiuretic hormone, serum cortisol, salivary cortisol, serum thyroid-stimulating hormone, urine osmolality, aldosterone, albumin and renin valves fell within the normal range. During worsened swelling and hyponatremia, urine osmolality ranged between 119 to 495 mOsm/kg, which ruled out the typical differential diagnoses for other causes of hyponatremia, with no clear explanation for her clinical findings and serum sodium.

Laboratory studies showed a high titer of antinuclear antibodies (1:2560), positive findings for SS-A/SS-B, mildly low C4, negative myositis antibodies and an increased creatine phosphokinase level. International normalized ratio, anti-double-stranded DNA, anti-C3, antiribonucleoprotein antibodies and aldolase levels were normal. Electromyography and muscle magnetic resonance imaging did not show myositis, though the patient reported myalgia. Skin biopsies of the leg and neck revealed interface dermatitis and spongiosis with a mixed perivascular inflammatory infiltrate. The neck biopsy also demonstrated an additional follicular infiltrate consisting of neutrophils, lymphocytes, histiocytes and eosinophils. MxA staining of both biopsies was diffusely positive, along with the expression of IL-4 and IL-31.Altogether, these findings suggested DM. 

DM can include spongiotic dermatitis. Further, DM has increased MxA, distinguishing it from the spongiosis of eczema.

Source: Grinnell M, Keyes E, Vazquez T, et al. Dermatomyositis associated with hyponatremia and anasarca. JAAD Case Rep. 2021;16:86-9.