An 8–year–old African girl presented to Muhimbili National Hospital, Dar es salam, Tanzania, with an 8 week history of recurrent fever, followed by a skin rash, weakness of all limbs, and generalized body swelling 2 weeks later. The fever was of low grade, accompanied by a sore throat, and was treated with antibiotics and antimalarial but it recurred with no specific periodicity throughout the course of her illness. The rash was maculopapular and itchy and started on the upper extremities (arms, hands and predominantly on the knuckles) and progressed to involve the thighs. This lasted for 2 weeks and persisted in the knees as papules and painful ulcerations on the flexure areas of the limbs. She developed a gradual onset of limb weakness, which was progressive and symmetrical, involving the proximal aspects of upper and lower limbs, and she was unable to comb her hair, climb stairs, and get up from squatting position. Weakness of limbs was accompanied by muscle and joint pain. She also noted swelling on the face, which was more prominent around the eyes. There was a reported nasal tone to her voice in the course of illness, but no history of dysphagia. There was no change in micturition habits. There was no history of night sweats, weight loss, or tuberculosis exposure. Otherwise she had a normal development and excellent school performance. She was the only child of nonconsanguineous parents. There was no family history of similar condition. She had already attended several hospitals, and been misdiagnosed and treated for various conditions with no improvement before coming to us.

On physical examination she was afebrile, in pain, with generalized edema (periorbital and bilateral nonpitting edema of upper and lower limbs). Her body mass index for age and sex was normal (16.3 kg/m2—median to + 1 SD). On local examination of the skin, she had hyperpigmented macules located on both knees, anteriorly more on the right, some coalesced to form patches on the knuckles (Gottron’s sign) (Fig. 1). There were also hyperpigmented patches and ulcers with clear crusted border margins measuring about 2 cm posterior to the knees and axillary folds (Fig. 2). She had a tiptoe gait with limited extension and flexion of the knees and ankle joint. Her grip power was normal with restricted movements of the elbows and shoulder joints. However, there was no joint swelling, warmth, or spine deformities noted. Her muscle bulk was normal but she had generalized tenderness in all muscle groups and a reduced power of grade 3/5 in proximal muscle groups of the upper and lower limbs with a positive Gowers’ sign. She had no calcinosis cutis. She scored 22/52 on Childhood Myositis Assessment Scale (CMAS-14).

Fig. 1
figure1

Lower limbs swelling with Gottron’s sign on both knees

Fig. 2
figure2

Ulcers with clear crusted margins on posterior aspects of both knees

Laboratory investigations revealed elevated serum levels of creatine kinase, 1948 U/l (29–168 U/l), lactate dehydrogenase [LDH, 1057 U/l (125–220 U/l)], aspartate aminotransferase [AST, 159 U/l (5–34 U/l)], C-reactive protein [CRP, 58 mg/l (0–5 mg/l)], erythrocyte sedimentation rate [ESR, 56 mm/hour (3–13 mm/hour)], thyroid stimulating hormone [TSH, 7.56 μIU/mL (0.49–4.67 μIU/mL)], normal free triiodothyronine (FT3, 1.81 ng/dl), and free thyroxine (FT4, 1.25 ng/dl). Full blood count and renal function tests were normal, Hepatitis B surface antigen (HBs Ag), Hepatitis C virus antibody (HCV Ab) were both negative. Magnetic resonance imaging (MRI) of the proximal legs showed increased signal intensity in muscular compartments seen as bright spots, signifying edema of the thigh muscles (Fig. 3). X-rays of the limbs and echocardiogram were normal.

Fig. 3
figure3

MRI of the proximal legs showing hyperintense signals

Based on the typical clinical features, laboratory and MRI findings, and subclinical hypothyroidism, the diagnosis of JDM with autoimmune thyroiditis was made.

The patient was treated with intravenous methylprednisolone at a dose of 30 mg/kg for 3 days followed by oral prednisolone at 60 mg/m2. An immediate dose of intravenous cyclophosphamide 500 mg/m2 was given, followed by weekly oral methotrexate 10 mg. Oral folic acid, calcium carbonate, omeprazole, and topical mupirocin were also given. The patient was initiated on daily physiotherapy.

Following treatment, the patient’s condition improved. Swelling and pain reduced first, subsequently weakness reduced, and she was able to walk longer distances, climb stairs with support, comb hair, and feed herself. Skin ulcers healed and she was able to extend her knees fully. However, the macules on the knee and ankle stiffness persisted.

She was discharged fairly well after 6 weeks to be followed-up in clinic and to continue treatment and physiotherapy.

At follow-up, on maintenance dose of 10 mg methotrexate weekly and daily folic acid at 5 mg/day, she fared well with gradual improvement in her muscle power, pain, and stiffness. She continued to have a tiptoe gait. She had good adherence to her treatment supported by her mother with no adverse effects to her regime.

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