Diagnosis: Neonatal lupus
This infant has neonatal lupus erythematosus, a rare syndrome in which maternal autoantibodies are passively transferred to the baby and cause cutaneous lesions or isolated congenital heart block. The skin rash generally appears a few days to weeks after birth, typically after sun exposure, and shows well-demarcated erythematous, scaling patches that are often annular and predominately on the scalp, neck, or face. It is self-limited and generally resolves without scarring by 6 to 7 months of age.
Differential diagnosis
The differential diagnosis of neonatal lupus syndrome includes annular urticaria, tinea corporis, seborrheic dermatitis, erythema annulare centrifugum, familial annular erythema, erythema multiforme, systemic lupus erythematosus, pityrosporum infection, and photosensitive genodermatoses.1 These can be differentiated from neonatal lupus by several defining characteristics:
- Annular urticaria is transient and pruritic
- In tinea corporis, a KOH prep reveals numerous branching hyphae
- Seborrheic dermatitis is characterized by greasy scales over red, inflamed skin and distributed in facial and body folds
- Erythema annulare centrifugum usually affects the trunks and legs; the characteristic rings enlarge daily
- Familial annular erythema is generally found on the back and shoulders and accompanied by a family history of similar lesions in infancy
- Erythema multiforme is more often on extensor surfaces and is uncommon in infancy
- Systemic lupus erythematosus should be suspected if the infant has the clinical manifestations or positive serological tests while autoantibodies are absent in the mother
- Pityrosporum infection can be diagnosed by hyphae and spores (“spaghetti and meatballs”) on KOH preparation
- Photosensitive genodermatoses are a rare group of disorders that are characterized by chronicity without autoantibodies.
Causes and pathophysiology of neonatal lupus
Neonatal lupus is caused by the IgG autoantibodies anti-Ro/SSA and anti-La/SSB, which pass from the mother to the fetus via the placenta, although anti-U1-RNP antibodies can sometimes cause the cutaneous manifestations of neonatal lupus.2 The mother may or may not demonstrate features of connective tissue disease at the time of birth. Lupus has a higher incidence in Asian women than in the overall US population.
Possible symptoms in the neonate include a characteristic skin eruption or congenital heart block. Neonatal lupus accounts for 85% of cases of congenital complete heart block diagnosed in utero or in the neonatal period.3 The incidence of complete heart block in offspring of women with anti-Ro/SSA or anti-La/SSB antibodies is about 2%. The incidence of complete heart block in infants with cutaneous neonatal lupus is 15% to 30%. Incomplete heart block, which may progress to complete heart block, may also occur. A less common and self-limited sinus bradycardia has also been described in fetuses.4
Other manifestations of neonatal lupus include thrombocytopenia, aplastic anemia, hepatobiliary dysfunction, and central nervous system vasculopathy.