Dermatology Case Study: Managing Onychomycosis In A Patient

Dermatology Case Study: Managing Onychomycosis in a Patient with Diabetes

Dermatology Case Study: Chief complaint: “My right great toe has been hurting for about 2 months and now it’s itchy, swollen, and yellow. I can’t wear closed shoes and I was fine until I started going to the gym.”

HPI: E.D., a 38-year-old Caucasian female, presents with complaints of pain, itching, inflammation, and a yellow discoloration of her right great toe. She reports noticing moderate itching after showering at the gym, which she initially dismissed. Approximately two weeks later, the itching intensified, and she applied Benadryl cream with partial relief. Over time, her symptoms worsened, and the toenail changed color, thickened, and turned completely yellow. The toe became swollen and painful. She also applied Lotrimin AF cream, which did not improve her symptoms. She has not tried other remedies.

Denies fever and chills. Medical history includes type 2 diabetes mellitus. She takes Metformin 500 mg twice daily. She is immunization up to date, including the flu shot. She consumes one glass of red wine nightly. She is a former smoker, quit six years ago. Family history includes father with type 2 DM and tinea pedis, and mother with atopic dermatitis and hypertension.

Review of systems reveals no respiratory distress, cardiac symptoms, or systemic malaise. On exam, vital signs are within normal limits, with BMI indicating obesity. The right great toe displays yellow-brown discoloration in the proximal nail, marked periungual inflammation, dryness, swelling, and tenderness. No pus or neuro deficits are noted. Pitting edema is observed in bilateral ankles.

Laboratory data show hemoglobin 13.2 g/dL, cholesterol 225 mg/dL, triglycerides 187 mg/dL, LDL 190 mg/dL, HDL 37 mg/dL, and fasting glucose 98 mg/dL. Fungal culture confirms fungal infection, supporting a diagnosis of proximal subungual onychomycosis, most likely caused by dermatophyte fungi.

Assessment

Primary diagnosis: Proximal subungual onychomycosis

Differential diagnoses include irritant contact dermatitis, lichen planus, and nail psoriasis.

Management and Prescription Recommendations

1. Antifungal Medication and Duration

According to the AAFP/CDC guidelines, oral terbinafine is recommended as the first-line systemic therapy for onychomycosis due to its effectiveness and superior cure rates (Welsh et al., 2014). Given the patient's diabetes, a systemic approach is indicated to ensure complete eradication of the fungal infection.

Approved antifungal medication: Terbinafine (Lamisil)

Prescription details:

• Medication: Terbinafine 250 mg tablets
• Dosage: 250 mg orally once daily
• Duration: 12 weeks
• Quantity: 84 tablets (to cover 12 weeks)
• Directions: Take one tablet daily with or without food. Complete the full course unless directed otherwise by the provider.

2. Baseline and Follow-up Laboratory Tests

Before initiating systemic terbinafine therapy, baseline laboratory assessments should include liver function tests (LFTs) and a complete blood count (CBC). Given the patient's history of diabetes and obesity, monitoring liver enzymes is essential to detect hepatotoxicity early (Gupta et al., 2019). Since terbinafine can cause hepatic adverse effects, baseline LFTs should be obtained, and follow-up testing should be scheduled at 4 to 6 weeks into therapy or sooner if symptoms develop.

Follow-up tests include:

• Liver Function Tests: ALT, AST, alkaline phosphatase, total bilirubin
• Clinical Monitoring: Assess for signs of hepatotoxicity such as jaundice, fatigue, or abdominal pain

If the patient develops symptoms suggestive of hepatic dysfunction or lab abnormalities, therapy should be discontinued, and further evaluation should be conducted. Additionally, given her diabetes, monitoring random blood glucose levels is prudent to observe for any effects related to systemic therapy.

Discussion

Onychomycosis is a common fungal infection frequently seen in adults, especially those with risk factors such as diabetes mellitus, immunosuppression, or peripheral vascular disease (Reich, 2019). The proximal subungual form, as seen here, is often associated with dermatophyte fungi and tends to be more invasive than distal forms, which underscores the importance of systemic antifungal therapy in such cases.

Terbinafine acts by inhibiting squalene epoxidase, disrupting fungal cell membrane synthesis, leading to fungal cell death (Gupta et al., 2021). Despite its high efficacy, it can cause hepatotoxicity, which warrants careful baseline and follow-up testing. The duration of therapy, typically 12 weeks, is based on the nail growth rate and the severity of infection (Lipsky, 2017).

Patient education regarding adherence, monitoring for adverse effects, and foot care is essential, especially considering her diabetic status. Proper foot hygience and avoiding trauma, along with regular podiatric evaluations, are also imperative in preventing recurrent infections (Wagenberg et al., 2018).

Conclusion

Effective management of onychomycosis involves systemic antifungal therapy, regular laboratory monitoring, and patient education. In this case, terbinafine 250 mg daily for 12 weeks is an appropriate first-line treatment, with LFTs and CBC monitored at baseline and periodically during therapy. Addressing underlying conditions such as diabetes and reinforcing good foot hygiene practices are crucial in preventing recurrence and complications.

References

• Gupta, A. K., Banerji, A., & Batra, R. (2019). American Academy of Dermatology guidelines of care for the management of onychomycosis. Journal of the American Academy of Dermatology, 80(4), 883-890.
• Gupta, A. K., Versteeg, S. G., & Shear, N. H. (2021). Systemic antifungal agents for onychomycosis. Journal of Fungal Infections, 15(2), 65-77.
• Lipsky, B. A. (2017). Fungal infections of the nails: Onychomycosis. Infectious Disease Clinics of North America, 31(2), 521-535.
• Reich, A. (2019). Onychomycosis: An update. Mycopathologia, 184(1), 69-81.
• Wagenberg, T. D. V., et al. (2018). Diabetic foot care and management of fungal infections. Journal of Diabetes Research, 2018, 1-10.
• Welsh, O. F., et al. (2014). Guidelines for the diagnosis and management of onychomycosis. Clinical Infectious Diseases, 59(1), 86-95.