What is the diagnosis for a 6-month-old girl presenting with irritability, listlessness, hypotonia, hepatosplenomegaly, protuberant abdomen, cherry red macula, and diminished deep-tendon reflexes, who has regressed from previously attained developmental milestones?

Differential Diagnosis for a 6-month-old Girl with Irritability, Listlessness, and Developmental Regression

• Single most likely diagnosis: + Neuronal Ceroid Lipofuscinosis (NCL): This condition, also known as Batten disease, is characterized by developmental regression, seizures, loss of motor skills, and visual impairment. The presence of a bright red macula is a hallmark of this disease. However, the age of presentation and specific symptoms can vary among the different forms of NCL.
• Other Likely diagnoses: + Krabbe Disease: A lysosomal storage disorder that leads to demyelination in the central and peripheral nervous systems. Symptoms include developmental delay, irritability, and regression of motor skills, which align with the patient's presentation. + Gaucher's Disease Type 2: An acute form of Gaucher's disease that presents in infancy with hepatosplenomegaly, developmental regression, and neurological symptoms. The presence of hepatosplenomegaly and neurological decline makes this a plausible diagnosis. + Tay-Sachs Disease: Another lysosomal storage disorder that affects nerve cells, leading to developmental regression, seizures, and a characteristic cherry-red spot on the macula. While the disease typically presents between 3 to 6 months of age, the symptoms can vary.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed): + Congenital HIV: Infection with HIV can lead to neurological symptoms, developmental delay, hepatosplenomegaly, and lymphadenopathy. Given the potential for vertical transmission and the severity of untreated HIV, this diagnosis must be considered. + Congenital Syphilis: Can cause a wide range of symptoms including hepatosplenomegaly, lymphadenopathy, and neurological abnormalities. The diagnosis is critical due to the availability of effective treatment. + Leukemia or Lymphoma: Although less common in infants, these malignancies can present with hepatosplenomegaly, lymphadenopathy, and systemic symptoms. Prompt diagnosis is crucial for treatment and prognosis.
• Rare diagnoses: + Niemann-Pick Disease: A group of lysosomal storage disorders that can present with hepatosplenomegaly, developmental regression, and cherry-red macula. The disease is rare and has various forms, making diagnosis challenging. + Pompe Disease: A glycogen storage disease that affects muscle cells and can lead to cardiomegaly, hepatomegaly, and muscular weakness. The infantile form is severe and presents early in life. + Mucopolysaccharidosis (MPS): A group of metabolic disorders caused by the deficiency of enzymes needed to break down sugar molecules. Symptoms can include developmental delay, hepatosplenomegaly, and clouded corneas, among others.