Lyme Disease

This 52 year-old woman presented as a walk-in patient today. She has a five day history of an erythematous nodule on the right shoulder which has developed a ring around it. The ring measures 9 by 11 centimeters in diameter. Initially, the nodule was painful for a few days; but the pain has subsided. She has had no fever or constutional symptoms and has continued to work as a school teacher.

The patient lives in rural New Hampshire and gardens a fair bit. She was seen two times at a primary care clinic where a diagnosis of spider bite was made. First she was given Keflex, then amoxicillin.

Diagnosis: I am uncertain. I favor Lyme Disease but this has atypical features. The central nodule is unusual, although the peripheral ring looks like Lyme. I also considered atypical Sweet's Disease and a pyogenic process. Lastly, I thought of eosinophilic cellulitis (Well's Syndrome) which I have never seen.

Plan: Since she feels well, I prescribed Doxycycline 100 mg bid, and ordered a cbc, Lyme titers and a G6PD (if the lesion becomes necrotic may want to try Dapsone. I considered biopsy but was strapped for time and thought Lyme most likely. Now, I am uncertain. Biopsy will be done when she is seen in follow-up unless she is significantly better.

Your thoughts will be welcome.



















Addendum:

Path Report:
DIAGNOSIS: Skin - (A) Right Shoulder-Periphery-Ring Surrounding Nodule:
Tight, mild superficial and deep perivascular lymphocytic infiltrate .
NOTE : These changes are those of a dermal hypersensitivity reaction to an exogenous antigen and, given the clinical presentation, are consistent with erythema chronicum migrans .

DIAGNOSIS: Skin - (B) Right Shoulder-Nodule:
Broad scale crust containing neutrophils , epidermal hyperplasia , marked papillary dermal edema and a superficial and deep perivascular and interstitial mixed inflammatory cell infiltrate composed of lymphocytes , neutrophils , histiocytes and plasma cells with rare eosinophils consistent with arthropod bite reactio n.
NOTE : These changes may be seen in a tick bite and erythema chronicum migrans . Clinico-pathologic correlation is suggested.

The Lyme Titer is positive.

In my opinion, this is not definitive, but the onus is on me at this time to continue to treat for Lyme.
The patient is on doxycycline and will continue on this at a dose of 100 mg bid for three weeks.
The patient reports that after three days of doxycycline the lesion is smaller. This, too, is not definitive, however, one can not ignore that either.


One Week Follow-up.
The patient feels better. Has mild insomnia.
Although initial lab titer was positive -- the Western Blot was negative indicating an early infection. Our infectious disease consultant expected them to be negative. Early treatment can prevent conversion. Will probably repeat in 2 weeks.

Picture on June 29, 2006