A Rash That Didn't Make Sense

As a pediatrician focusing on adolescent medicine, I almost took the dermatology path but realized that the cases I was seeing in a primary care practice were more challenging than the referral cases my dermatology colleagues were seeing… and more fun, too.

I have never claimed to be a dermatologist… just a pediatrician (with the gift of a photographic memory) who on my own and with a lot of assistance learned and maintained a more than fundamental knowledge of pediatric, adolescent, and some adult dermatology.

I am a lifelong student (just as you should be) and often refer to myself as a PGY 43 (this year) who enjoys sharing what I have learned with my primary care colleagues and believes that the learning process should be both informative and fun.

In a recent case, we had the satisfaction of making the diagnosis of dermatomyositis in a 7-year-old girl who presented with muscle weakness and an unusual rash.

A Very Weak Young Girl with a Rash

A 7-year-old boy with a recalcitrant rash appeared to have dermatomyositis. However, he did not have: fatigue or muscle weakness, difficulty swallowing, joint swelling.

With the mother's consent, we ordered basic laboratory work and I consulted with a rheumatology colleague.

Muscle biopsy, EMG, and MRI were not ordered. Lab studies ordered were: ESR, CBC with differential, SGOT, SGPT, LDH, CPK, rheumatoid factor, ANA, Anti Jo1 antibody, EKG

An image of the patient's face: Note the reddish-blue bumps

Note reddish-blue lichenified papules on his knuckles, some ulcerated; also note mild erythema around the cuticles. I was certain these were Gottron’s papules.

Laboratory values/results were all WNL thus not suggestive of dermatomyositis. But my rheumatology colleague had confirmed my suspicions.

What is the most likely diagnosis? Rheumatoid arthritis, discoid lupus, a vitamin deficiency, dermatomyositis with normal labs, none of these

Diagnosis: Amyopathic dermatomyositis.

Characterized by presence of dermatomyositis for ≥6 months in persons who have normal muscle enzymes, no clinically significant muscle weakness. Muscle involvement may be delayed for several years.

Multiple studies indicate that in children the prognosis is far from clear. In one large study of children followed for ≥18 years 19% developed malignancies before age 18 but majority never had anything more than cutaneous findings.

For the current patient we refer to rheumatology for further evaluation and maintain close contact for all other health matters. Tests now required: MRI studies of large muscle groups, EMG, muscle biopsies, repeat labs.

This case did not end as we would have liked. Parents refused further testing and the child was lost to follow up after returning to his native Philippines.

Myopathic dermatomyositis has been classified more recently as a subset called clinically amyopathic dermatomyositis (CAMD). A 2006 systematic review offers an excellent parsing of this

“missing link in the spectrum of idiopathic inflammatory myopathies.”

Many diseases present as a spectrum; we had to investigate what didn’t make sense in the face of pathognomonic skin findings. In primary care, we should always be ready to learn more.

We can save time and cost by being thorough in the beginning or by going back to basics when we reach an apparent dead end. It's good for our patients and good for our own job satisfaction.