Steven Pfeiffer syndrome pedigrees (three 3 generation and four 2 generation) 
have been recorded to date in addition to at least a dozen sporadic cases. 
Autosomal dominant inheritance with complete penetrance is characteristic of the 
7 familial instances. Variable expressivity has involved mostly the presence or 
absence of syndactyly and the degree of syndactyly when present. Classic 
Pfeiffer syndrome is designated type I. Type 2 consists of cloverleaf skull with 
Pfeiffer hands and feet together with ankylosis of the elbows. Such patients do 
poorly with an early death. All reported instances to date have been sporadic. 
Type 3 is similar to type 2 but without cloverleaf skull. Ocular proptosis is 
severe in degree and the anterior cranial base is markedly short. These patients 
also do poorly and tend to have an early death. To date all cases have occurred 
sporadically. Although these 3 clinical subtypes do not have status as separate 
entities, their diagnostic and prognostic implications are important. Type 1 is 
commonly associated with normal intelligence, generally good outcome, and can be 
found dominantly inherited in some families. Types 2 and 3 generally have severe 
neurological compromise, poor prognosis, early death, and sporadic occurrence. 
Recognition of type 3 is particularly important because extreme ocular proptosis 
in the absence of cloverleaf skull but with various visceral anomalies can 
result in failure to diagnose Pfeiffer syndrome and labeling the patient as an 
"unknown" or as a "newly recognized entity."(ABSTRACT TRUNCATED AT 250 WORDS)