Leprosy As a Mimicker for Systemic Autoimmune Diseases

Summary: Leprosy As a Mimicker for Systemic Autoimmune Diseases Gizem Gokalp, MD.1, Omar Tolaymat, MD.2 1. Fellow at University of Florida, Division of Rheumatology & Clinical Immunology 2. Faculty at University of Florida, Division of Rheumatology & Clinical Immunology No Disclosures Background Leprosy is a chronic infectious disease caused by the bacterium Mycobacterium leprae. While it primarily affects the skin and peripheral nerves, it can also present with a wide range of systemic symptoms, often mimicking various autoimmune diseases. Skin lesions can resemble those of sarcoidosis, while mononeuritis multiplex, recurrent fever, and lymphadenopathy may mirror manifestations seen in vasculitis. We present a case initially suggestive of a systemic rheumatological disorder, which ultimately proved to be associated with leprosy. Case Presentation A previously healthy 22-year-old Cuban male presented with recurrent fevers persisting for over a year, lymphadenopathy, and distal neuropathy. The patient immigrated from Cuba, traveling mostly on foot through Central America and passing through mountains en route. A few days after his arrival, he developed a rash on his left forearm (image 1-2) and began experiencing fevers up to 104°F with recurrent bilateral inguinal lymphadenopathy. Despite multiple visits to urgent care where he was prescribed doxycycline, his symptoms relapsed within 10 days of each treatment course. Further evaluation at an outside hospital included inconclusive biopsy of lymph nodes and negative flow cytometry for malignant cells. After a year of persistent symptoms, the patient acutely developed left hand weakness and numbness. He denied any history of sick contacts, cat scratches, or consumption of undercooked meat, though he did report experiencing testicular pain and swelling lasting one month prior to hospital presentation. There was no pertinent family history of autoimmune disease or malignancy. Physical examination revealed a fever of 103 °F, left wrist drop, a coin-like skin rash on the right arm, and bilateral inguinal lymph nodes enlargement. Initial extensive workup failed to identify the etiology for his disease. These evaluations included tests for ANCA with MPO/PR3, ANA, SSA/SSB, CSF studies, blood cultures, HIV, EBV, CMV, HTLV1/2, Brucella, Lyme, Bartonella, Q fever, and QuantiFERON. Patient’s labs were remarkable with CRP at 258. Nerve conduction study revealed mononeuritis multiplex. Skin biopsy showed erythema nodosum leprosum with perivascular, perineural lymphohistiocytic infiltrate with neutrophils. Patient is discharged with rifampin, moxifloxacin, minocycline, methotrexate 20 mg weekly and prednisone tapering. Discussion Musculoskeletal manifestations in leprosy can mimic various diseases including rheumatoid arthritis, spondyloarthropathy, reactive arthritis, psoriatic arthritis, vasculitis, sarcoidosis, and gout. We got this consult after the diagnosis of mononeuritis multiplex. The broad differential diagnosis for mononeuritis multiplex includes inflammatory conditions such as sarcoidosis, systemic lupus erythematosus, and rheumatoid arthritis, vasculitis, infectious etiologies like Lyme disease, HIV, hepatitis B/C, and leprosy. Additionally, evaluation should consider amyloidosis, and malignancies. Nerve damage in leprosy can also be attributed in part to vascular involvement. Leprosy type reactions are immunological responses complicating the infection's course. Type 1 Reaction involves enhanced cell-mediated immunity, worsening existing lesions and nerve damage. Type 2 Reaction is immune complex-mediated, presenting with fever, nodules, arthritis, and vasculitis. Our patient had type 2 reaction, which prompts management with methotrexate and prednisone. The number of reported leprosy cases has more than doubled in the southeastern states over the last decade. According to the National Hansen’s Disease Program, 136 new cases were reported in the United States in 2022; Florida was among the top reporting states. Central Florida accounted for 81% of cases reported in Florida and almost one fifth of nationally reported cases. Conclusion Given the overlapping clinical features between leprosy and systemic autoimmune diseases, a thorough evaluation, including a detailed medical history, physical examination, and laboratory tests, is essential for accurate diagnosis. We believe our case offers guidance for future similar cases. References 1. Marc C. Hochberg, MD Rheumatology. Available from: Elsevier eBooks+, (8th Edition). Elsevier - OHCE, 2022. 2. Gupta L et al. Leprosy in the rheumatology clinic: an update on this great mimic. Int J Rheum Dis. 2016 Oct;19(10):941-945. doi: 10.1111/1756-185X.13023. PMID: 27792872.