Case History/ Examination:

A 24-year-old normotensive, non-diabetic, non-asthmatic male from Chandpur was admitted to a tertiary medical hospital in Dhaka in May 2024 with a ten-month history of gradually worsening multiple joint pain. The pain began in the small joints of the hands and feet and later involved the shoulders. He also presented with hyperpigmented patches of varying sizes and shapes over the scalp, extensor surfaces of the elbows, dorsum of the hands, back, extensor thighs, knees, and feet. These lesions were initially erythematous and scaly without oozing, discharge, or bleeding upon scratching. Scalp hair loss and unintentional weight loss of 25 kg were also noted over the past eight months, accompanied by a reduced appetite, but no gastrointestinal or cardiopulmonary symptoms. Low-grade, intermittent fever (maximum 101°F) had persisted for six months, along with generalized weakness over four months, leading to difficulties in squatting, sitting up, and climbing stairs, requiring assistance for daily activities. Six months prior to this admission, the patient had been treated for ”Psoriasis with Psoriatic arthropathy” with methotrexate, sulfasalazine, topical calcipotriol, steroids (betamethasone), and urea. However, treatment complications, including methotrexate-induced oral mucositis, necessitated medication changes. Sulfasalazine was discontinued after two weeks due to recurrent mucositis, and “Apremilast” was initiated, although it provided minimal relief for joint pain. The patient denied any history of eye pain, photosensitivity, genital ulcers, chest pain, or breathlessness, as well as any significant systemic or infectious history, including TB contact or recent travel. He had no significant family medical history, substance use, or risky sexual behavior. His immunization, including for COVID-19, was up to date. Upon examination, the patient appeared ill, moderately anemic, and underweight, with a BMI of 14.8 kg/m². Skin inspection revealed multiple hyperpigmented patches on the extremities and trunk (Figure 1A-C), without scaling in most areas. There was diffuse scarring alopecia (Figure 1D), particularly over the scalp. Notably, an erythematous patch with silvery-white scales was observed on the back of the trunk (Figure 2). Musculoskeletal examination showed swelling, tenderness (Grade-IV), hyperpigmentation, and raised temperature over the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of both hands (Figure 3), accompanied by dorsal guttering and wasting of the thenar and hypothenar muscles. Shoulder abduction was painful and restricted bilaterally (Figure 4), while hip movements were similarly painful and limited. Neurologic examination was unremarkable, but needle electrode examination (NEE) indicated asymmetric sensory neuropathy, consistent with mono-neuritis multiplex, with early signs of myopathy or neuromyopathy. Methods (Differential diagnosis, investigations and treatment): Upon admission, a comprehensive diagnostic approach was undertaken to address the patient’s complex presentation. A skin biopsy conducted nine months prior revealed hyperkeratosis, parakeratosis, Munro’s abscess, and dilated capillaries in the dermal papilla, consistent with psoriasis. Further evaluation of the patient’s reduced muscle bulk and power led to a muscle biopsy, which showed mild variation in muscle fiber diameter, internalized nuclei, and scant inflammatory infiltration, suggesting muscular dystrophy. Initial laboratory investigations revealed normocytic normochromic anemia (hemoglobin: 9.3 g/dL), leukopenia (WBC: 3640/mm³), thrombocytopenia (90,000/mm³), elevated ESR (46 mm/h), and creatine phosphokinase (307 U/L). Notably, ANA was moderately positive, and anti-CCP levels were low positive (17.98 U/mL), along with severe vitamin D deficiency (9.1 nmol/L). Imaging studies of the chest, spine, and pelvis showed mild osteopenia, with normal ECG and echocardiography findings. Given the overlapping clinical features, differential diagnoses included rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), dermatomyositis, and mixed connective tissue disease (MCTD). However, the negative ENA (Extractable nuclear antigen) profile and muscle biopsy findings excluded dermatomyositis and MCTD. Based on the American College of Rheumatology (ACR) criteria, with 9 out of 10 points, the patient was diagnosed with RA, supported by joint involvement, elevated ESR, low-positive Anti-CCP, and symptoms persisting for more than six weeks. Additionally, the presence of positive ANA, pancytopenia, non-scarring alopecia, and synovitis aligned with SLE. Psoriasis, confirmed via skin biopsy 9months ago, further complicated the case. Ultimately, a diagnosis of ”Rhupus” overlap syndrome was made and undifferentiated connective tissue was kept as alternative differential. The patient was treated with prednisolone 20mg (0.5mg/Kg) and hydroxychloroquine 200mg (5mg/Kg), targeting RA and SLE. Psoriasis was managed with topical therapies, and muscular dystrophy was addressed through supportive care, including physical therapy. Vitamin D(40,000IU) supplementation was initiated to correct the deficiency.   Conclusion and Results (Outcome and follow-up): In conclusion, diagnosing “Rhupus” overlap syndrome is inherently challenging, requiring thorough exploration and exclusion of other autoimmune conditions when patients present with non-specific symptoms beyond their primary disease. Our patient, initially diagnosed with psoriasis, benefited from this comprehensive approach, which allowed for a more holistic treatment strategy. This resulted in both patient satisfaction and a favorable prognosis. During a follow-up two months later, the patient showed marked improvement, including better shoulder abduction (Figure 5), weight gain (BMI: 16.3 kg/m²), and a reduction in joint line tenderness from grade 4 to grade 1.