A 22 year old African-American woman presents with a butterfly-shaped rash and bilateral arthritis. What is the most likely condition?

The presence of a butterfly-shaped rash, also known as a malar rash, is strongly indicative of Systemic Lupus Erythematosus (SLE). This type of rash specifically appears across the cheeks and over the bridge of the nose, resembling the shape of a butterfly, and is one of the hallmark signs of this autoimmune disease.

Additionally, bilateral arthritis is commonly seen in SLE, further reinforcing the likelihood of this diagnosis. SLE is more prevalent among young women and individuals of African-American descent, making this patient's demographic details relevant and supportive of the diagnosis.

In contrast, while rheumatoid arthritis can also present with joint pain and inflammation, it does not typically cause the characteristic rash associated with SLE. Parkinson disease and amyotrophic lateral sclerosis (ALS) primarily affect motor function and do not present with either of these signs. Thus, the combination of a butterfly rash and arthritis distinctly points toward Systemic Lupus Erythematosus as the most probable condition in this scenario.