Each month, this department features a discussion of an unusual diagnosis in genetics, radiology, or dermatology. A description and images are presented, followed by the diagnosis and an explanation of how the diagnosis was determined. As always, your comments are welcome via e-mail at email@example.com.
The patient is a 10-year-old, previously healthy Hispanic boy who presented with severe pain in his toes for 3 years. The patient described the pain as burning associated with warmth of the toes but no erythema, bluish discoloration, or swelling. He reported that massaging his feet or immersing them in cold water ameliorated his pain slightly.
His review of systems, including other joint aches, blurring in vision, skin changes, headaches, fever, night sweats, weight loss, abdominal pain, and urinary symptoms, was negative. The first time he was seen at our clinic, his parents brought X-rays of his feet, which were taken in Mexico and which were read as normal. As per the patient’s parents, there haven’t been recent stressors, school difficulties, or behavioral problems to explain their son’s severe pain.
Initial workup included erythrocyte sedimentation rate (ESR) (1); CRP (within normal range); ANA (negative); rheumatoid factor (negative); C-anca (< 6) and P-anca (< 6); a complete blood count; and thyroid function tests, all of which were normal (Free T4:1.4). Fasting blood sugar and an oral glucose tolerance test were also ordered. Results were within normal range (fasting sugar: 77; 1-hr glucose level: 66; 2-hr glucose level: 55). The patient was advised to take over the counter non-steroidal anti-inflammatory medications (NSAIDs) and to continue conservative measures.
Over the next few months, his pain became so intolerable that a hospital admission was warranted. A neurologist recommended a nerve conduction velocity testing at that time to rule out peripheral neuropathy. This was again reported as normal. He was discharged on gabapentin, which seemed to improve his pain thereafter.
The patient was finally seen by a rheumatologist, who made the diagnosis of erythromelalgia (EM) based on symptoms, negative workup, and response to gabapentin. This was a diagnosis of exclusion, as so far there is no reported test to confirm it. He continued on gabapentin with improvement in his symptoms to date. His mother reported that as a child, she had the same type of pain, but that her pain slowly improved over the years.
When the patient presented for the first time to our clinic, our differential diagnosis included rheumatoid arthritis; systemic lupus erythematosus; diabetic neuropathy; peripheral neuropathy; psychosomatic pain; Raynaud’s disease; and erythromelalgia (see Sidebar). A rheumatologic disease was ruled out by the negative ANA, C-anca and P-anca and by the absence of other symptoms suggestive of arthritis, such as swelling and stiffness of joints.
Rheumatological diseases (rheumatoid arthrotis, systemic lupus erythematosus, scleroderma, Rayndaud’s disease, erythromelalgia)
Neurological diseases (peripheral neuropathy, diabetic neuropathy)
His fasting blood sugar and 2-hr OGTT were normal, which ruled out diabetic neuropathy. Nerve conduction velocity testing failed to reveal evidence of peripheral neuropathy. Raynaud’s disease presents with cold-induced pain, bluish discoloration, swelling of toes, and improvement of pain with immersion in warm water. Our patient’s pain improved with immersing his toes in cold water. The patient had severe pain in his toes, but no swelling or erythema, which made the diagnosis of erythromelalgia inconclusive initially.
Erythromelalgia is a rare, chronic, debilitating condition characterized by redness, warmth, and severe burning pain of the distal extremities. The feet are more commonly affected than the hands. Pain is precipitated by increases in temperature and by exercise. Patients often obtain relief by immersing the affected extremity in cold water.1 Flaring typically occurs…